SHLOMO NAVARRO

Stored crops: the search for food security.

Shlomo Navarro

Growing crops and protecting them until used for consumption has been a major preoccupation of mankind since the inception of agriculture. Storage is an essential interim operation in the food pipeline that moves crops from producer to processor and foodstuffs from processor to consumer. It equilibrates the quantitative fluctuations derived from the imbalance of supply and demand.
The human population as the major consumer cereal food and pulse crops was estimated to be about 5.3 billion in 1990 and projections are 6.1 billion in 2000 and 8.1 billion in 2025. Although in developed countries dependence on cereals for food energy has decreased, populations of 53 developing countries still derive 40% of all food energy from cereals. The present demand has caused reduction in world cereal stocks, especially in the major export countries. Global food production has scarcely kept pace with increase in demand. Surpluses in the industrialized countries are in striking contrast to the food shortages in many developing countries and there is still a threat of famine to countries where natural disaster and internal strife combine to destroy the agricultural infrastructure. Hunger today may be threatening the lives of about 800 million people in the developing world, with approximately 60% of them living in Asia. People may suffer from food shortage or malnutrition, especially in the poorest countries where agricultural production is never in surplus, where facilities for storage are lacking, and in regions subject to extreme climatic fluctuations from one year to the next.
Durable foodstuffs with their low moisture content form the basis for most human diets precisely because these commodities can be stored for extended periods and are continuously available provided that there is no insect infestation. However, losses occur at every stage of food handling and storage. These losses may be either quantitative or qualitative. The magnitude of losses is highly variable and in certain cases they may even reach 100%. Qualitative losses are more difficult to evaluate then quantitative ones. Qualitative losses for example, may consist of changes in the physical appearance, nutritional degradation, loss of germination, presence of fragments and insect infestation, contamination by mold or development of mycotoxins. Some of them are difficult to detect visually.
In developed countries qualitative aspects of food loss are of greater importance than the quantitative ones. In these countries cereal grains are stored in large centralized storage facilities or on-farm in bulk. Under these conditions quantitative losses are generally at low levels so that further loss reductions are not cost effective. Losses of biological origin such as grain or insect respiration, or limited drying due to aeration of grain in storage are common. These losses on an annual basis are usually less than 1%.
Developing countries are characterized by small scale farming where deficiencies in handling and storage methods, and very often warm and humid climatic conditions promote rapid deterioration of the stored foodstuffs. In developing countries the major portion of grain and pulses (sometimes up to 80% of the national production) is kept on the farms for home consumption. Postharvest losses of food grain in developing countries have been conservatively estimated during the 1980s at 10-15% by the FAO's Special Action Programme for the Prevention of Food Losses. For example, losses of corn due only to insects in farmers' stores in Nigeria, Swaziland and Kenya, were in the order of 6-10%.
A major effort over recent decades has been devoted to improving storage conditions of cereal and pulse crops, and reducing losses in tropical countries. Past attempts at introducing "state-of-the-art" storage structures into several developing countries for this purpose have met with failure and are witnessed by many such "white-elephants" standing empty and abandoned. However, more appropriate storage systems have also been widely introduced, and have enabled the successful transfer and updating of modern conservation and control technologies with consequent reduction in storage losses.
Reduction of storage losses at the small-scale and subsistence farmer levels has proved to be far more difficult than in the commercial or public sectors. This is because the available storage conservation technologies are costly and not applicable to most of the traditional storage methods unless radical changes are made. Therefore new solutions must be found, appropriate to the local conditions, and acceptable to the societies into which they are to be introduced.
In spite of the advances recorded in many fields of modern agriculture and particularly a changing approach to pest control, fumigation has remained a mainstay for control of stored product insects by conventional methods. However, it is worth noting that of the 14 fumigants listed some 20 years ago, only two remain today in regular world wide use namely; phosphine and methyl bromide. Methyl bromide (MB) is characterized by its lethal effect within very short exposure times, such as 4h to 24h, and the fact that insect resistance to this fumigant has not been recorded in the field. In contrast phosphine is a relatively new fumigant that is extremely popular, particularly in developing countries, because of its ease of application in comparison with methyl bromide. It is characterized by the distinct disadvantage of requiring long periods of exposure, with a minimum of five days now being recommended. A serious threat to this fumigant is the increasing number of recordings of insects that have developed resistance over the last decade.
Methyl bromide is regarded as the main anthropogenic compound that depletes the ozone layer. It is widely used as a fumigant in agriculture, for pest control in structures, stored commodities and quarantine treatments. Its main uses are for soil sterilization (about 72% of total usage), disinfestation of perishables (9%), disinfestation of durables (14%), and against pests in structural fumigations (5%). Presently there is no available alternative to MB for short-exposure fumigations.
Development of alternatives to MB are likely to be costly and many developing countries will not be able to afford evaluations of these alternatives without assistance. According to the Montreal Protocol Programme of 1995 the decision for developed countries is a phase-out by year 2010, with stepped reductions commencing in 2001, whereas for developing countries there will be a freeze in use in 2002, based upon an average of the quantities used over the period 1995 to 1998. The position of the signature countries to the Montreal Protocol with regard to developing countries will be reviewed again in 1997. Under present agreements, there are exemptions for all countries from controls on methyl bromide when used for quarantine and pre-shipment fumigations, and for some critical agricultural uses, yet to be defined.
Contact insecticides may provide persistent protection against reinfestation. They can be applied directly to grain, but they are not normally registered for use on processed foodstuffs. Contact insecticides include synthetic chemicals, insect growth regulators, plant extracts (botanicals) and inert dusts. One major constraint associated with their use is the presence of chemical residues in the treated commodities. Resistance also is a major problem, while the high cost of registration is a constraint to the development of new products.
Among the non-chemical alternatives, physical control methods play an important role. These include the use of modified atmospheres, heat, irradiation and physical removal of insects. Treatment with controlled or modified atmospheres based on carbon dioxide and nitrogen offer a potential alternative to fumigation with toxic gases for insect control in all durable commodities. As a general rule cold treatments are not used for disinfestation of large masses of durables. A major problem encountered is the time needed to cool such masses. For this reason, cooling is used generally to prevent reproduction and reinvasion of pests in grain bulks by applying aeration and refrigerated aeration for cooling, rather than as a disinfestant. Heat treatment is one of the very few pest control options for grain that is capable of matching the speed of treatment afforded by MB. Fluid bed heating systems for bulk grain have been developed to a commercial prototype stage.
The electro-magnetic spectrum also offers a series of possibilities. The two extreme ranges, namely long wave radio frequencies and ionizing irradiation have detrimental effects on insects, whereas medium wavelengths especially in the range of visible light are used for insect monitoring purposes. Irradiation is already in use commercially for shelf-life extension of some fresh commodities and for disinfestation. The food industry is concerned about consumer acceptance of irradiated food products. The large initial capital expenditure for plant construction also poses a serious constraint.
Physical removal of insects, sanitation and improved packaging methods should all be regarded as means to assist pest control in stored commodities. Biological methods, including the use of microbiological control agents and pheromones are at an early stage of implementation. Although pheromones are being used increasingly for monitoring purposes, their widespread application as control measures is not expected in the near future.
On the level of international cooperation, further support is needed to fund appropriate R&D activities with the objective of transferring and adapting already proven technologies to developing communities. To enhance technology transfer, the extension activities in developing countries should be encouraged.
Priorities for future research on protection of stored crops should concentrate on the following topics: a) development of appropriate technologies for developing countries; b) development of non-chemical control methods; c) development of novel pesticides based on biotechnological approaches; d) further development of IPM strategies and; e) evaluation of new fumigants and other alternatives.
There is a continuing need for research on a broad front. Alternatives for treatment of durables for reducing fumigant emissions should include: a) revision of dosage rates to avoid overdosing; b) improvement of gastightness of enclosures and c) reducing the frequency of treatments by preventing or reducing reinvasion of pests subsequent to fumigation.
This has been directed mainly towards storage at the national or para-statal level, or grain belonging to the commercial sectors and commercial farmers.
Although a large variety of potential alternatives to MB for disinfestation of durable commodities have been suggested, some of these will require considerable development in both laboratory and field before they can be introduced into routine disinfestation systems.

Outdoor Storage of Corn and Paddy Using Sealed-Stacks in the Philippines

Shbmo Navarro, Jonathan E Donahaye, Filipinas M. Caliboso and Glory Sabio

The applicability of using sealed stacks for modified atmosphere or gastight storage of paddy and corn stacked in the open in the Philippines was investigated. Heavy duty plastic was used to provide a solution to short and medium term preservation of dry paddy and corn at the farmer and farmer-cooperative level. A series of experiments was carried out in Israel to develop the plastic structures. It included studies on permeabilities of plastic sheeting to oxygen and carbon dioxide, and resistance to insect and rodent penetration. Investigations in the Philippines comprised storage under modified atmospheres (MA) using CO₂ flushing of corn and biogeneration of MA using gastight storage of corn and paddy without gas replacement. Carbon dioxide flushing treatments proved effective for insect control but the low availability of CO₂ cylinders limits this approach at present. Moisture migration was observed in all the trials. The use of agricultural wastes provided insulation from diurnal temperature fluctuations and was effective in preventing moisture migration for up to 4 months storage under Philippine conditions. The trials showed that gastight storage provides an acceptable protection by maintaining the number of live insects below the threshold of economic damage without the need for pesticides.

A sealed granary for use by small-scale farmers

Shlomo Navarro, Jonathan Donahaye, A. Guray Ferizli, Miriam Rindner and Avi Azrieli

A sealed granary was designed and tested for on-farm storage of harvested grain by small-scale farmers to provide food security for rural communities. It has the advantage of sealed storage that obviates the need of employing residual insecticides and fumigants. The granary, designed to hold 540 kg nominal capacity of grain, consisted of a gastight cylindrical flexible plastic bag. It was equipped with an upper conical collapsible sleeve for loading and a flexible sleeve for unloading. It was inserted into a rigid white polypropylene board curved into a cylinder that forms a sheath surrounding the vertical sides of the flexible bag. To prevent accumulation of rain-water on top of the bag, it was kept suspended beneath a horizontal strut. During unloading, the bag collapsed progressively so that the volume of headspace remained minimal. Artificially infested maize at a moisture content of 10.3% was tested. Insect survival, gas composition and temperature of the maize was measured. Oxygen concentrations dropped to 5.5% within 40 days. Maize temperatures were within the range of 36°C to 26°C . In spite of favorable temperatures for development of insects, at the end of two months storage and during the 6 weeks unloading, the initial populations of Tribolium castaneum and Rhyzopertha dominica were successfully controlled without the use of pesticides.

Pressure tests for gaseous applications in sealed storages: theory and practice

Shlomo Navarro

Pressure tests and monitoring devices described in this paper apply to structures destined for gaseous treatments to control principally insects in durable agricultural commodities including cereals. The gaseous treatments included here are: modified atmosphere (MA), controlled atmosphere (CA) and fumigation. These pressure tests are designed to estimate the permissible limits for effectively maintaining the gas composition in small, medium and large size warehouses and silos during the treatment. They are not capable however of measuring gas losses that occur by permeation through structural membranes such as concrete and plastic. Theoretical work to describe the process of gas loss from structures is well documented. This paper reviews essential considerations in measuring gastightness. However field work to correlate gas loss to pressure tests are very scarce. The described pressure tests in this paper are applicable for rigid and flexible types of structures. Variable and the constant pressure tests are fully described. In the variable pressure test. time is taken for the pressure to fall between two pressure limits while in the constant pressure test, the flow rate at a given constant pressure is measured. A table is presented for provisional ranges of the variable pressure tests to be applied in structures destined for MA, CA and fumigant treatments.

Control of nitidulid beetles in dried fruits by modified atmospheres

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli

Among the important pests of dried fruits are nitidulid beetles. Infestation starts in the field and unless control measures are employed, they and other pests continue to multiply and develop during storage. Methyl bromide (MB) has been used for fumigating dried fruits. However, because it is associated with the depletion of the atmospheric ozone, action has been taken to phase out its use in agriculture. This work was undertaken to develop a modified atmosphere treatment which would remove insects from the dried fruit. Dates grown in Israel served as a model for development of the technology. Laboratory experiments were carried out to investigate the influence of different modified atmospheres (20% carbon dioxide in air or 2.8% oxygen in nitrogen), low pressures alone or MB alone in causing Nitidulid beetles to emigrate from infested dried fruit for which dates served as a model. At 4 h exposure and at 26°C, the treatments that had a marked influence in causing insects to abandon the infested fruit were: low pressure of 100 mm Hg and 2.8% oxygen in nitrogen, all of which caused over 80% of the initial insect populations to emigrate from the fruit.

Application of modified atmospheres under plastic covers for prevention of losses in stored grain

Shlomo Navarro, and Filipinas M. Caliboso

The objective of this project was to provide temporary or emergency storage facilities for use for small scale farmers and intermediary organizations after unusually favorable growing seasons, or where security reserve stocks are required yet permanent storage structures are lacking. The project incorporated an evaluation of the applicability of using flexible liners developed in Israel for modified and hermetic atmosphere storage of paddy and corn stacked in the open and so to develop an affordable storage system for small-scale farmers, farmer cooperatives, and intermediary storage organizations in the Philippines and elsewhere. The storage cubes and silos manufactured from the flexible liners were intended to provide an inexpensive solution to short and medium term preservation of dry and intermediate moisture content grain, by protection from biological agents without the need for use of pesticides. The study consisted of a series of preliminary trials in Israel with prototype liners, followed by a series of trials during the second and third years of the project, in the Philippines, with storage of "intermediate moisture content" paddy rice and corn. The Philippine investigations comprised both storage under modified atmospheres using carbon dioxide flushing, and hermetic storage without gas replacement. The phenomenon of moisture migration due to temperature gradients within the grain bulks was studied in Israel. The trials were accompanied by laboratory studies on the permeability of liners to gases (Israel), resistance of liners to insect penetration (Israel and the Philippines), and resistance to rodent penetration (Israel). A preliminary model was developed to simulate the interdependent changes in gas concentrations, dynamics of insect population and amounts of grain consumed. Numerical experiments were run to investigate the degree of gas-tightness of the structure expressed as permeation rate of oxygen through the storage membrane, size of grain mass, volume of the storage structure, number of initial insects/kg of grain, respiration rate of the insect population, birth and death rates of the different species, and the amounts of grain consumed. This model was developed to enable prediction of safe storage periods under the different physical and biological variables described above. The trials and accompanying laboratory studies showed that the flexible PVC storage cube and silo are technically feasible for outdoor storage of paddy and corn. The technology shows strong potential for adoption in the postharvest operation of farmer cooperatives, private traders and millers who process their produce. In particular, development of hermetic storage should be viewed as an alternative technology to CO₂ enriched atmospheres in view of the frequent non-availability of CO₂, particularly of food-grade. Rodent penetration trials confirmed the findings that the cubes provided an effective barrier to rodents when correctly set-up. Also the PVC liners were shown to be highly resistant to insect penetration. Although the CPE had lower permeability to gases than the PVC liners it was more susceptible to insect and rodent penetration, more susceptible to welding failures and was also susceptible to abrasion. Use of agricultural wastes in the trials of both countries to provide insulation from diurnal temperature fluctuations in the cube proved to be effective in preventing moisture migration and microbial spoilage.

The future of hermetic storage of dry grains in tropical and subtropical climates

S. Navarro, J.E. Donahaye and S. Fishman

Oxygen (O₂) depletion and carbon dioxide (CO₂) enrichment of the intergranular atmosphere form the basis for suppressing and controlling insect infestations during hermetic storage of dry grain. Traditional methods and recent improvements are reviewed, and modem structures designed for hermetic storage at the commercial and farmer levels are described. Improvements needed to render the hermetic concept more widely acceptable are enumerated and the development of hermetic storage within flexible plastic liners is evaluated on the basis of more than a decade of experience in hot climates. A preliminary model is employed to simulate the interdependent changes in gas concentrations, insect populations and amounts of grain consumed. A theoretical ingress rate of 0.05% O₂ /day was found sufficient to arrest development of residual insect infestations. Potential niches for hermetic storage applications in developing and technologically advanced countries are identified. In tropical climates aeration for cooling of grain is not feasible, reinfestation is frequent and the available contact insecticides degrade rapidly because of high temperatures. The advantages of long-term hermetic storage in technologically advanced countries, and as a medium-term, user-friendly technology in developing countries, are stressed. In sharp contrast to the use of chemicals, hermetic storage is environmentally sound and poses no risk to storage operators, consumers or non-target organisms.

Preservation of grain by airtight storage

Shlomo Navarro and Ezra Donahaye

Preservation of grain quality in storage systems sufficiently airtight to control insects is reviewed. These systems are being used for long-term storage, as well as intermediate grain storage, especially for centralized storages, cooperatives and the small scale farmer. The principle of the systems is based on the use of airtight synthetic liners. The structures investigated included bunkers for bulk storage of thousands of tonnes of grain, and silo of up to 1,000-tonne capacity with wall support of weld-mesh fencing. For capacities of up to 50 tonnes of bagged grain, specially designed envelopes termed storage cubes have been developed. All these structures are recommended for dry grain storage only.

Application of Modified Atmospheres in grain storage: Retention of Carbon Dioxide within treated enclosures

Shlomo Navarro, Ezra Donahaye and Hovav Talpaz

Abstract - A numerical model to simulate the influence of the different factors that affect gas behavior within a treated enclosure was outlined. The model was compared with experimental results obtained on concentration changes measured in two silos treated with carbon dioxide. The silos were of the same dimensions: one contained 52 tons and the other 28 tons of wheat. Changes in carbon dioxide concentrations, grain and ambient temperatures were recorded periodically throughout the trials. Results of the measured gas concentrations in the trials were compared with the calculated gas concentrations obtained from the numerical model and found to fit satisfactorily. Several numerical experiments were run to simulate the influence of different head space/total volume ratios, pressure relief valve settings, and degrees of gas tightness. The model may be used as a tool in grain storage management to estimate the most important factors which influence gas loss, and to assess the need for improvements in the gas tightness of the treated structure.

Preservation of grain in hermetically sealed plastic liners with particular reference to storage of barley in Cyprus

Shlomo Navarro, Andreas Varnava and Ezra Donahaye

In Cyprus, barley of 10% moisture content (m.c.) was stored on two concrete platforms covered with PVC liners. The floor of one platform was lined with polyethylene on which about 4,000 tonnes of barley were stored 'for 9 months. On the second platform, 2,500-tonnes of barley were loaded directly on the concrete and stored for 7 months. Insect activity was controlled in the first platform within four months, but in the second platform was only partially suppressed. Moisture content remained stable except for the peak layer, where moisture migration caused a marked increase. Mold damaged barley unfit for consumption was 0.0088% and 0.1874% of the total quantity in the first and second platforms, respectively. Germination remained above 95% throughout the storage periods. In Israel 15,567 tonnes of wheat of approximately 11% m.c. were stored for 15 months in a bunker bordered by earthen ramps using a PVC overliner and polyethylene underliner. Insect activity was suppressed and tota1 damage from insects and molds were estimated at 0.15 and 0.06%, respectively. Moisture migration to the peak layer, particularly in thc region of higher initial m.c., necessitated removal of damaged grain and affected germination and baking quality in that area. Elsewhere, germination averaged 95% and loaf volume was not lower than that of wheat under usual storage conditions.

Commercial quarantine fumigation of narcissus bulbs to control narcissus flies

S. Navarro, E. Donahaye, R. Diaz, Miriam Rindner and A. Azrieli

Fumigation trials were carried using methyl bromide (MB) to control narcissus flies in bulbs destined for export. The objective was to increase fumigation efficiency by utilizing two gastight fumigation chambers (fumigation bubbles) in order to reduce the danger of phytotoxic damage by applying the minimum effective dose required to kill the insects. It was found that for the 4 h exposure regime required for quarantine purposes, recirculation was necessary to produce initial uniform concentrations. Dosage in the 48 m³ and 102 m³ capacity bubbles (without inflation) had to be adjusted to take into account both the volume of free space within the bubbles and sorption by the bulbs. MB concentrations recorded by thermal conductivity (TC) monitors were influenced by the CO₂ concentrations generated from bulb metabolism during fumigation. With recirculation in the 48 m³ bubble, an initial dosage of 25 g m^-3 resulted in stabilization of MB concentrations after 90 min at close to 20 g m^-3. This concentration is close to the LD99 of Merodon eques as evaluated in laboratory studies.

Induced tolerance of Sitophilus oryzae adults to carbon dioxide

S. Navarro, R. Dias and E. Donahaye

Sitophilus oryzae adults were exposed to 40% carbon dioxide (CO₂) in air for seven successive generations and to 75% CO₂ in air for ten successive generations at 26deg C and 100% relative humidity (r.h.). The tolerance factor (LT95 selected generation/LT95 non-selected generation) at the 7th generation of insects exposed to 40% CO₂ was 2.15 and at the 10th generation exposed to 75% CO₂, was 3.34. Reduction of the r.h. to 60% in the 75% CO₂ atmosphere caused shortening of exposure times required to obtain the same mortality values, but the tolerance factors remained stable. Removal of selection pressure for five generations of the 40% CO₂ and four generations of the 75% CO₂ selected strains caused significant reduction in tolerance. Augmentation of oxygen concentration to 21% in atmospheres containing 40 and 75% CO₂ did not markedly alter the tolerance factors from those obtained with atmospheres containing the same CO₂ concentrations in air.

Plastic structures for temporary storage of grain

Shlomo Navarro and Ezra Donahaye

A gastight container consisting of a UV-resistant PVC liner and a welded wire mesh fence was evaluated for grain storage. The container was also equipped with an aeration system to permit grain cooling and reduce risks of moisture migration. Storage of 1000 tonnes of wheat grain was monitored over nine months. Tests were carried out to determine gastightness of the container, gas composition of the intergranular air, grain moisture, temperature, the presence of insects, and germination power of wheat over the storage period. The grain bulk had an initial temperature of 25°C and a moisture content of 11% (wb). Insect population levels were low but these gradually increased causing a reduction in oxygen level to 8.5% within four months. After seven months of storage, grain moisture content remained stable except for a marginal increase at the peak of the container. Germination of the major part of the grain bulk remained above 90% throughout the storage period and insect damage was negligible. The feasibility of using such containers in the humid tropics is discussed.

Integration of controlled atmosphere and low temperature for disinfestation and control of dried fruit beetles

Shlomo Navarro, Ezra Donahaye, Miriam R1ndner, Raphael Dias and Avi Azrieli

Nitidulid beetles are important pests of dried fruits, particularly dates at the time of harvest. Upon arrival at the packing stations, dates are disinfested by fumigation. This treatment serves a twofold purpose of stimulating the active insect stages (larvae and adults) of field infestations to abandon the fruits and also killing all stages of the insect population. Experiments were carried out to investigate the effect of various modified atmospheres (MAs) and low pressures alone in prompting the emigration of Nitidulid bectles from infested dried fruit, for which dates served as a model. The most effective treatments were pressure of 100 mm mercury (Hg) and 2.8% oxygen (O₂) in air, both of which caused over 80% of the initial insect populations to emigrate from the fruit after a 4 hr exposure. However, the MA treatments required longer exposure times to achieve complete mortality as compared with standard fumigation procedure. An alternative approach to controlling the insects after disinfestation by MAs was by storage at low temperatures. Exposure to -5°C caused relatively slow kill. Pupae were the most resistant stage, necessitating approximately 90 hr to produce 99% kill (LT99) of Carpophilus mutilatus Er and Carpophilus hemipterus L. Exposure to -18°C caused very rapid kill of both species, LT99 of all stages being obtained within 2.25 hr.

Generation and Application of Modified Atmospheres and Fumigants for the Control of Stored Insects

S. Navarro and E. Donahaye

Modified atmosphere (MA) and fumigation treatments are carried out to create an environment lethal to insects in stored commodities. The sole alternative to fumigation for in-storage insect control which also offers a diversity of applications and toxic-residue-free treatment is the MA method. This paper reviews what are currently the most frequently used methods for generation and application of MAs and fumigants. MAs can be generated from liquefied gas, bulk transported in road tankers, or delivered from cylinders for small-scale treatments. The alternative approach is on-site generation of MAs. This includes the use of exothermic gas generators based on combustion of hydrocarbon fuel, and the use of air compressors and molecular sieves to produce nitrogen from air. Possibilities for on-site generation of MAs from biological sources, including assisted hermetic storage by external biogeneration of MAs, as well as conventional hermetic storage, are also discussed. The effects of MAs on most common storage insects have been studied in relation to concentration and exposure time in order to establish dosage schedules. These show that carbon dioxide-air atmospheres are usually more toxic than oxygen-deficient ones. The methods of application and their gas supply requirements are reviewed in relation to the constructional limitations of the existing enclosures to be treated. Fumigants are produced and marketed in containers convenient for application, either in liquid state in pressurized cylinders, or in solid-state formulations. Methods of generation for the most commonly used fumigants, namely methyl bromide and phosphine, and for various fumigant mixtures are discussed. Fumigant application using gravity penetration, grain stream admixture, assistance from recirculation, and vacuum and space techniques, all of which continue to be widely used, are critically reviewed.

Airtight storage of wheat in a P.V.C. covered bunker

S. Navarro, E. Donahaye, Y. Kashanchi, V. Pisarev and O. Bulbul

Wheat of 11.4% moisture content was stored in an airtight enclosure formed by a polyethylene liner at its base and with a UV-resistant P.V.C. sheet over the surface. The wheat bulk of 15,566.5 t was supported by 2 m high earth banks. The oxygen concentration fell to 6% and the carbon dioxide concentration increased to 9% within 3 months. Insects were present only in the part of the upper layer where the wheat moisture content and high germination and baking quality was preserved. Wheat damage attributed to insects was estimated at 0.15%, and that to moulds at 0.06%. The P.V.C. liner remained in good condition and retained its elasticity, and no rodent damage was detected.

Sensitization of insects to fumigation techniques including reduced pressure

S. Navarro and E. Donahaye

The unique properties and inherent advantages offered by fumigation for controlling storage insects are under careful reconsideration because of the occurrence of insect resistance to fumigants, and restrictions related to the undesirable effects of fumigant residues. Mixtures of fumigants have been investigated with the aim of potentiating the toxic action against insects. However, since the number of approved fumigants has been reduced over recent years, increasing attention has been devoted to methods that employ physical means for sensitizing the insects to fumigant action. The effect of carbon dioxide in enhancing the toxicity of fumigants has been investigated on several stored-product insects. The use of carbon dioxide - fumigant mixtures is desirable to reduce both the length of the exposure period and the pesticide residue levels in the treated commodities. In studies carried out using methyl bromide (MB)-carbon dioxide mixtures the susceptibilities of test insects have been found to increase by a factor of about two. For the fumigation of dried fruit in fumigation chambers turn-over time and toxic residue levels are both critical factors that require optimization. Currently, "vacuum" fumigation is widely employed to achieve these objectives. Laboratory fumigations for up to 18 hours of larvae, pupae and adults of two species of Carpophilus (Coleoptera: Nitidulidae) which are major pests of dates in the field and in storage in Israel, revealed differences in sensitization between MB fumigation in a 20% CO₂ atmosphere and MB fumigation at 100 mm Hg. Sensitization to Mg by CO₂ was in the order of x2 to x3 for 18-hours exposure of C. hemipterus, while maximum sensitization by 100 mm Hg was x1.5 at 18 hours exposure. For C. mutilatus maximum sensitization to MB by CO₂ was x2.1 (for adults). At 2 hours' exposure differences in sensitization were marginal, while for more prolonged fumigations CO₂ was generally more effective than 100 mm Hg. The significance of these findings is discussed.

Quality conservation of paddy stored under gastight seal outdoors in the Philippines

S. Navarro, Filipinas M. Caliboso, Glory Sabio and E.J. Donahaye

Paddy stacks of capacities ranging from 13.4 to 31.9 t were stored outdoors in flexible enclosures for 78 to 183 d. The quality of the paddy was compared with that of three control stacks (5.3-5.6 t capacity) held under tarpaulins in the open for 78-117 d. The trials were conducted at the NAPHIRE compound, Nueva Ecija, the Philippines. Two varieties of enclosures were tested, heavy-duty PVC-based sheeting sufficiently gastight to control insect infestations (called "Volcani cubes" and designed in Israel for stacked bag storage) and weld-mesh supported silos, in both of which the paddy was stored in bulk. In both systems, the upper layers of paddy were covered with a layer of rice hulls aimed at reducing temperature gradients, and plastic sheeting was placed between this insulating layer and the grain, serving to prevent the transfer of moisture to the top grain layer. Moisture content, grain temperature and gas concentrations were measured throughout the trials. Initial and final samples were taken to determine changes in paddy quality; insect infestation, fungal infection, milling recovery, head rice, yellow kernels, brokens, germination and weight loss were analyzed. The percentage of milling recovery and the levels of yellowing in the gastight stacks showed no significant change. The levels of head rice and brokens were preserved in seven out of nine stacks. A decrease in the percentage of head rice in two stacks was attributed to the biological aging phenomenon. The two control stacks showed a decrease in head rice and an increase in brokens. Rice yellowing was very pronounced in one of the control stacks.

Can diapausing larvae of the khapra beetle be controlled using CO₂ or vacuum?

s. Navarro, e. Donahaye, r. Dias a. Miriam rindner and azrieli

Although there is a large number of suggested potential alternatives to MB for disinfestation of durable commodities, development of most of these alternatives is likely to be costly. The combined factors of mb phase-out, the gradual development of insect resistance to fumigants and the undesirable effects of fumigant residues in food, have led to the idea of using controlled atmospheres. The objective of this investigation was to develop an alternative control treatment based on vacuum or a combination of heat and CO₂.
Response of insects to low pressures is temperature and moisture dependent. It was demonstrated that at 25°C and 65% relative humidity complete mortality of adults of most common storage insect pests was obtained within 7 h when exposed to 20 mm Hg. However, among storage insects, diapausing Trogoderma granarium larvae were found to be the most resistant species, for which under the same conditions, a 120-h exposure was necessary. To control the diapausing larvae of T. granarium within a 72-h exposure time it was necessary to increase the temperature to 30°C.
CO₂ concentration and temperature levels were investigated using diapausing larvae of T. granarium as test insects. The influence of CO₂ at 45°C on reducing the exposure time expressed as LT95 (hours to obtain 95% mortality) values for T. granarium showed that by increasing the CO₂ concentration to 90% the exposure time decreased to about 8 hours. These results demonstrate the potential use of CO₂ in combination with heat as an alternative control method to MB.
These encouraging reports led to the idea of developing a transportable system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15 m³ capacity plastic container termed the volcani cube. This container is made of a flexible liner and characterized by its transportability. An oil-lubricated vacuum pump (3 hp) to reduce the pressure to 25-mm Hg within 25 min was used. The purpose of the tests was to study the technology that would contribute to improved performance. The possibility of maintaining low pressures within 22 and 75 mm Hg in the Volcani cube over extended periods that may last several months was tested.

Reducing MB dosage or exposure time using CO₂ with MB or CO₂ with heat

S. Navarro, E. Donahaye, Glory C. Sabio, Miriam Rindner, R. Dias and A. Azrieli

This study was undertaken to investigate the effect of methyl bromide (MB) in combination with CO₂ with the objective of reducing MB dosages to minimum effective levels, and consequently minimizing MB emissions. In addition, a combination of a CO₂ with heat as an alternative treatment to MB was investigated. Dosage levels were investigated using all four developmental stages of the almond moth, Ephestia cautella (Walker). For control of the egg stage, the influence of CO₂ in reducing the effective mb concentration, expressed as concentration x time (ctp) in mg.h/l, was marginal, but it was most pronounced for larvae, pupae and adults. Addition of CO₂ decreased the MB ctp values for larvae and pupae to half, and for adults to one third compared to MB without CO₂. The influence of CO₂ at 40°C on reducing the exposure time expressed as LT95 (hours to obtain 95% mortality) values for E. cautella showed that the most sensitive was the adult, and the most resistant was the pupal stage. Increasing the CO₂ concentration to 80% decreased the exposure time to about 10 hours for the most resistant pupal stage. These results demonstrate the potential use of CO₂ in combination with heat as an alternative control method.

Critical limits of sealing for successful application of controlled atmosphere or fumigation

S. Navarro and L. Zettler

A fundamental requirement for the successful application of gaseous treatments to control stored-product insects is a well-sealed structure. A fumigatable flexible structure for outdoor storage of stacked commodities of 7.5 m³ was used to demonstrate the critical limits of degree of sealing using the variable pressure test. Time in minutes for the half-life pressure decay was correlated with daily ventilation rates of O₂, CO₂, phosphine and methyl bromide. The ventilation rates were tested using different size of cross section leak areas with orifices of 1.6 mm, 3.2 mm and 6.4 mm i.d. To evaluate the influence of temperature on the rate of gas exchange, the cube was tested when it was under cover by providing shading, to minimize direct solar heating effect, and when it was exposed to direct solar heating.
O₂ infiltration rate for modified atmospheres was 0.5% O₂/day at 5 min half-life pressure decay when the cube was under shade. For the same level of gastightness gas loss was 0.8% O₂/day when exposed. CO₂ loss rate was 2%/day at 5 min half-life pressure decay when the cube was under shade and 3%/day when the cube was exposed. Loss rate of phosphine from the cube for the shaded conditions was 100 ppm/day at a 3-min half-life pressure decay time. A sealing equivalent to 4.5 min half-life pressure decay time was required when exposed. The methyl bromide loss rate of 1.0 g/m³/day was equivalent to about 5 min half-life pressure decay time. At the time tests were carried out with methyl bromide, ambient temperature differences were not large enough to show different loss rates between the shaded and the exposed cube.

Disinfestation of nitidulid beetles from dried fruits by modified atmospheres

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli

Among the important pests of dried fruits are nitidulid beetles. Infestation starts in the field and unless control measures are employed, they and other pests continue to multiply and develop during storage. Methyl bromide (MB) has been used for fumigating dried fruits. However, because it is associated with the depletion of the atmospheric ozone, action has been taken to phase out its use in agriculture. This work was undertaken to develop a modified atmosphere treatment which would remove insects from the dried fruit. Dates grown in Israel served as a model for development of the technology.
Laboratory experiments were carried out to investigate the influence of different modified atmospheres (20% carbon dioxide in air or 2.8% oxygen in nitrogen), low pressures alone or MB alone in causing nitidulid beetles to emigrate from infested dried dates. At 4 h exposure and at 26°C, the treatments that had a marked influence in causing insects to abandon the infested fruit were: low pressure of 100 mm Hg and 2.8% oxygen in nitrogen, both of which caused over 80% of the initial insect populations to emigrate from the fruit.

Application of modified atmospheres in grain storage: retention of carbon dioxide within treated enclosures

S. Navarro, E. Donahaye and H. Talpaz

A numerical model has been developed to simulate the influence of the various factors that affect gas behavior within a treated enclosure. Model predictions were compared with experimental measurements of concentration changes in two silos treated with CO₂. The silos were of the same dimensions but one contained 52 tons and the other 28 tons of wheat. Changes in CO₂ concentrations, grain and ambient temperatures were recorded periodically throughout the trials. Results of gas concentration measurements in the trials were compared with the calculated values obtained from the numerical model and found to fit satisfactorily. Several numerical experiments were run to simulate the influence of different head-space/total-volume ratios, pressure relief-valve settings, and degrees of gas tightness. The model may be used as a tool in grain-storage management, to estimate the most important factors which influence gas loss, and to assess the need for improvements in the gas tightness of the treated structure.

Integration of modified atmospheres for disinfestation of dried fruits

S. Navarro, E. Donahaye, R. Dias and E. Jay

The effects of reduced atmospheric pressures alone, methyl bromide (MB) alone, and combinations of MB with CO₂ and with reduced pressures, to increase sensitivity of all development stages of Carpophilus hemipterus and C. mutilatus were investigated. The effectiveness of non-chemical treatments for removing Carpophilus species larvae from naturally and artificially infested dates was tested by exposing the larvae to low pressures, high temperatures, and modified atmospheres (MA), while MB served as a chemical disinfestation treatment for comparison.
A method based on the use of artificial refuges was devised to simulate the infested dates. It was demonstrated that both the chemical and non-chemical treatments tested have the potential to exert a state of stress in the insects which appears to cause Carpophilus larvae to abandon the host.

The influence of temperature and moisture content on the germination of peanut seeds

S. Navarro, E. Donahaye, R. Kleinerman and H. Haham

Shel1ed and in-shell peanut seeds (cvs. 'Hanoch' and 'Congo') were stored at different moisture contents at 15, 20 and 26°C in an apparatus designed to purge air at relative humidities in equilibrium with the moisture contents of the seeds. Storage lasted nearly 6 months during which the moisture contents and germination percentages of the seeds were examined periodically.
The result of germination trials showed significant differences between in-shell and shelled seeds for the cv. 'Hanoch' but not for cv. 'Congo'. The calculated moisture content required to maintain 90% germination for shelled seeds stored for 6 months at 15°C was 8.0% For 'Hanoch' and 7.9% for 'Congo'. To conserve the same germination level for 6 months at 26°C the calculated moisture contents were 7.1% For both 'Hanoch' and 'Congo'.

Integration of modified atmospheres for disinfestation of dried fruits

S. Navarro, E. Donahaye, R. Dias and E. Jay

The effects of reduced atmospheric pressures alone, methyl bromide (MB) alone, and combinations of MB with CO₂ and with reduced pressures, to increase sensitivity of all development stages of Carpophilus hemipterus and C. Mutilatus were investigated. The effectiveness of non-chemical treatments for removing Carpophilus species larvae from naturally and artificially infested dates was tested by exposing the larvae to low pressures, high temperatures, and modified atmospheres (MA), while MB served as a chemical disinfestation treatment for comparison.
A method based on the use of artificial refuges was devised to simulate the infested dates. It was demonstrated that both the chemical and non-chemical treatments tested have the potential to exert a state of stress in the insects which appears to cause Carpophilus larvae to abandon the host.

Control of the wax moth by environmentally sound methods

S. Navarro, Y. Slavetski, E. Donahaye, B. Jacobsen, M. Rindner and A. Azrieli

The wax moth is a major pest of stored honeycombs, and periodic control treatments are essential. Until now these have been undertaken by fumigation. However, because of the reduction in the number of available fumigants, and limitation of this treatment to licensed operators, an alternative, environmentally friendly control method, was developed. This consisted of treatment in a CO₂-enriched atmosphere, in plastic tents designed to hold the beehive supers and honeycombs. The tents are then kept hermetically sealed to prevent reinfestation during the storage period.

Aeration of grain as a non-chemical method for the control of insects in the grain bulk

S. Navarro

Low temperature ranges that suppress development of stored-grain insects are reviewed. Possibilities of cooling grain bulk either by aeration with selected ambient air or refrigerated air are considered. Use of aeration with ambient air in temperate climates and in countries having a cool season is reported. Some examples of the studies carried out under British and Australian climates are discussed.
Data are presented on observations carried out in Israel. A wheat bulk of 1142 tonnes aerated with ambient air resulted in reduction of grain temperature from 32.2°C to 10.5°C. During storage over 22 months the grain remained free from insect development.
Trials conducted with refrigerated air showed that under summer conditions a bin containing 699 tonnes of wheat was cooled from 30-37°C to 18-19°C during 160 hr. The presence of a live insect population in the bin appeared to be responsible for a gradual rise in temperature. In a similar bin cooled from 30-34°C to 16-19°C, insect infestation was lower and the subsequent temperature rise was also less pronounced. Under the reported climatic conditions, the trials indicated that cooling with refrigerated air could be achieved throughout the year and at a higher rate of cooling than by aeration with selected ambient air.
It is shown that sufficient cooling to prevent insect infestation can be obtained and this method seems to be most efficient when the initial insect population is very low. However, possible changes in the biology and composition of the stored products fauna should be envisaged due to the alteration of the microclimate of the grain bulk.

Mode of action of low atmospheric pressures on Ephestia cautella (Wlk.) pupae

S. Navarro and M. Calderon

The influence of low atmospheric pressures and low oxygen concentrations on 0-24-h-old Ephestia cautella (Wlk.) pupae at 26°C was determined. Effects on respiration, insect mortality and loss in weight obtained, were due to low oxygen tension only, at both normal and low atmospheric pressure.

Studies on aeration with refrigerated air- I. Chilling of wheat in a concrete elevator

S.NAVARRO, E.DONAHAYE and M.CALDERON

Two-hundred and forty-five tonnes of wheat in a concrete vertical bin were cooled by aeration with chilled air from a chilling unit (with a cooling capacity rated at 42,500 kcal/hr) to prevent development of insect populations. Initial temperatures of 21-21.5°C were lowered after 94 hr of cooling to 9.9-12.7°C. Under the ambient conditions the rate of cooling was limited by the aeration system of the bin. Cooled air entering the bin was at relative humidities higher than those in equilibrium with the grain moisture content and this caused moistening of grain around the aeration duct to above the critical level for safe storage under local conditions. A re-heater incorporated in the unit designed to reduce relative humidity of the cooler air was inefficient for the cooling of dry grain and reduced the cooling efficiency of the unit.

The effect of carbon dioxide anesthesia on the lactate and pyruvate levels in the hemolymph of Ephestia cautella (Wlk.) Pupae

. Navarro and A. Friedlander

1. Ephestia cautella (Wlk.) pupae were exposed for 24 hr to controlled atmospheres containing 20-89% carbon dioxide, and to reduced oxygen tensions (from 21 to 1 per cent) at 95-100% R.H. and 26°C.
2. A steady rise was observed in the lactic acid level: from 6.06 ml hemolymph (control) to 74.25 mg/ 100 ml at an atmosphere containing 89% carbon dioxide. Decreasing oxygen concentrations left the lactate levels close to the control value, but below 3 per cent a sudden rise of lactate, reaching 287.98 mg/ 100 ml hemolymph at 1% oxygen, was found.
3. Pyruvic acid levels remained around 3. 84 mg/100 ml (control) throughout the changes in carbon dioxide tension. A change in pyruvate level was noticed only at 1% oxygen, when the value became 7.47 mg/100 ml.
4. Lactic dehydrogenase activity in whole tissue of controls was found to be 30.4 Wroblewski units/mg protein, while treated pupae showed an average activity of 30.9 units/mg, which proves that LDH activity is unaffected by treatments.
5. No LDH activity whatsoever could be located in the hemolymph.

Studies on aeration with refrigerated air-II. Chilling of soybeans undergoing spontaneous heating

S. Navarro, E. Donahaye and M. Calderon

A cooling trial was carried out on 229 tonnes of soybeans at 14 per cent moisture content stored in a vertical concrete bin in Israel during the summer of 1971. During this period two cycles of heating were recorded and heating foci reaching temperatures of 47 and 41°C respectively, were cooled by aeration using a chilling unit of 42,500 kcal/hr capacity. The two cooling passes resulted in moistening of grain around the aeration duct, and a slight overall drying effect on the soybean bulk. Germination remained stable except around and above the heating foci. Energy consumption required for conservation of the soybeans from early February until late August was about 9 kW/hr/t, and the bulk was at each pass cooled to around 20°C at rates of 121 and 112 t/24 hr.

Exposure of Ephestia caute1la (Wlk.) (Lepidoptera, Phycitidae) to Low Pressures: Effects on Adults

. Navarro and M. Calderon

Adults of Ephestia cautella (Wlk. ) were exposed to pressures of 100, 200, 300, 400 and 760 mm Hg at 26 ± 1°C and 70 % r.h., in a specially designed apparatus in which a controlled atmospheric gas composition was maintained. Adult life was shortened at all reduced pressures, at 100 mm Hg all adults died in 14 hr. Oviposition was affected at reduced pressures resulting in a significant reduction in the number of eggs laid. At 100 mm Hg oviposition was negligible. A hypothesis to explain these observations is mentioned.

Observations on Prolonged Grain Storage with Forced Aeration in Israel

S. Navarro, E. Donahaye and M. Calderon

Observations were carried out for 22 months on 1142 tonnes of wheat stored in a metal bin equipped with an aeration system and a fan withdrawing air at a rate of 5150 ft3/min. The observations comprised temperature measurements of the grain bulk, records of the ambient temperature and humidity and of the hours of fan operation, and examination of grain condition as indicated by moisture content, germination, insect infestation, and the percentage of damaged grains.
The observations showed that during the first year beginning in May 1966, 1212 hr of aeration lowered the temperature of different layers of the grain bulk from averages of 26.8-32.2°C to 10.2-13.8°C. During the summer of the second year the grain temperature rose to averages of 18.1-19.2°C. During the second winter of storage, 523 aeration hr cooled the grain bulk to averages of 10.5-14.3°C. The grain remained in excellent condition throughout the almost 2 years storage period.

Conservation Of Wheat Grain In Butyl Rubber/EPDM Containers During Three Storage Seasons

S Navarro and E Donahaye

Wheat grain was stored in 30 containers of 1,000-ton capacity each, during three storage seasons (1972 - 1975). The containers consisted of a butyl rubber/EPDM welded liner inside a circular supporting weldmesh wall, and were designed to provide an hermetic seal. The maximum storage period during a season was 13 months. Temperature and gas concentration of the bulks, moisture content of grain, and air-tightness of the liner were measured; insect presence was recorded. Operation of the aeration system caused a drop in bulk temperature to below 20°C in 25% of the measurements carried out in December. During the storage period an increase occurred In moisture content of grain at the top of the bulk; 48% of the samples from this region had a moisture content above 13%. Most of the samples drawn from other parts of the bulk remained at their original moisture content. The bulks were fumigated with phosphine gas at a dose of 750g/1,000 tons. The insects found were Cryptolestes sp., Oryzaephilus surinamensis L., Tribolium castaneum (Herbst), Sitophilus oryzae L. and Rhyzopertha dominica F. Sixty per cent of the samples examined during September were infested with live insects; following fumigation, this level was reduced to 18%, as detected in December. The number of live insects per sample of grain reached 118 during October and was reduced to six in November. The insect population remained low until the end of the storage period. Grain was preserved at a satisfactory level throughout the storage seasons.

From the CRC Press flyer:

An In-Depth Overview of Grain Storage Technology Throughout the World - Published Collectively For the First Time

The Mechanics and Physics of Modern Grain Aeration Management

Shlomo Navarro, Ph.D.
Senior Research Scientist
Agricultural Research Organization/The Volcani Center,
Department of Stored Products, Bet Dagan, Israel

Ronald T. Noyes, P.E., Ph.D.
Oklahoma State University,
Biosystems and Agricultural Engineering department,
Stillwater, Oklahoma USA

Of worldwide interest to those involved in production, handling, storage, and marketing of grain and oilseeds

Health and environmental regulations that resulted in the loss of many chemical pesticides used until recently and the ban on methyl bromide (associated with the depletion of atmospheric ozone), have generated the need for alternate technologies to solve grain storage problems. Aeration-improves stability of grain and greatly reduces the dependence on pesticides harmful to food and the environment This book will help those involved in the handling and processing of grain, provide food stuff that is free of toxins, insects, pesticides, and chemical residues.

The Mechanics and Physics of Modern Grain Aeration Management demonstrates the most advanced theoretical solutions and practical approaches to aeration as it affects grain storage science and technology that will be required for effectively cooling grain, for controlling storage insects and improving the storability of grain commodities, while minimizing residual pesticides.

This volume provides the necessary knowledge for aerating properly and efficiently within the context of new regulatory demands worldwide.

Features

Discusses the development of supplementary aeration methods for chemical fumigation application involving a special low gas volume recirculation system in line with the global trend to phase out methyl bromide use.

Treats alternatives for normal commercial aeration versus specialized aeration methods and techniques based on diverse climatic conditions

Offers a cross-disciplinary appeal to agricultural engineers, technicians, entomologists and crop scientists/agronomists

Describes unique specialized aeration processes such as "dryeration" that enhances drying and "grain chilling" for cooling high value crops.
Contents

Objectives of Aeration - S. Navarro
Ambient Air Properties in Relation to Aeration - G. Thorpe
Physical Basis of Aeration - G. Thorpe
The Aeration System - D. Jayas and W. Muir
Chilling of Grain by Refrigerated Air - D. Maier, S. Navarro, and R. Noyes
Experimental Aeration Systems Performance - R. Noyes, S. Navarro, and D. Armitage
Operating Aeration Systems - R. Noyes, S. Navarro, G. Thorpe, and J. Desmarchelier
Operating Specialized (Supplementary) Aeration Systems - R. Noyes, S. Navarro, G. Thorpe, and D. Maier
Evaluating Aeration System Efficiency - G. Thorpe and S. Navarro
Modeling of Air Distribution in Aeration - G. Thorpe, D. Jayas and W. Muir
CRC Press Catalog no. 1355 c. 550p ISBN: 0-8493-1355-4

Storage of Prunes Under controlled Atmospheres for Quality Preservation and Insect Control

Shlomo Navarro
The major objective of the studies summarized in this report was to investigate economically feasible alternatives to methyl bromide for control of dried fruit insect pests in general and of prunes stored in California in particular. Laboratory studies included tests on the equilibrium relative humidity, the metabolic activity of prunes for modified atmosphere storage, and a demonstration of the critical limits of leakage rates on the effectiveness of modified atmosphere and conventional fumigation.
Experiments to determine moisture content of prunes showed that, even at extended drying times over 152 h, a constant weight could not be achieved. This indicates the difficulty in determining the absolute moisture content of prunes and that any reported values are highly variable depending on the test method.
The feasibility of using self-generated atmospheres based on the metabolic activity of prunes was investigated. However, prunes dried in commercial dehydrators at elevated temperatures are physiologically dead and do not respire. Respiration processes from the microorganism load and their particular composition on the fruit do occur when the water activity of the fruit is above 0.755. This water activity value, also known as the equilibrium relative humidity, is equivalent to a moisture content of 29% in the case of prunes.
Experiments determined that microorganisms on prunes would flourish and cause deterioration of the fruit if the water activity of the fruit is above 0.70 (moisture content of 24.6%). However, in sealed structures (like the Volcani Cube) it was shown that prunes can be stored safely when water activity is as high as 0.65 (22% moisture content) without microorganism growth and deterioration of the fruit. Fruit samples taken from commercial storage bins showed that prunes are typically dried for 18 hours to a water activity of about 0.575 (15% moisture content) prior to storage. Samples taken during the drying process showed that prunes reached 0.65 water activity (22% moisture content = safe storage moisture content) after only 11.5 hours of drying. These experiments show that the drying process for prunes could be shortened significantly, with concomitant savings in dryer costs. These 'partially dried' prunes can then be safely stored in sealed structures like the Volcani Cube, perhaps relying on the self-generated atmosphere or a modified atmosphere to prevent insect and microorganism deterioration. This strategy could eliminate the need for conventional fumigation.
Half-life pressure decay times, based on several different leak rates, were determined for fumigants and modified atmospheres contained in the Volcani Cube. Experiments showed that the following gas exchange rates were the critical values for maintaining a sufficiently gas tight chamber: N₂ atmosphere, 0.5% O₂/day infiltration rate with a 5 min half-life; CO₂, 2%/day loss with a 5 min half life; phosphine, 100 ppm/day loss with a 3 min half-life; and methyl bromide, 1.0 g/m³/day loss with a 4.5 min half-life. Gas exchange rates greater than these critical values would be too costly in gas maintenance or would likely result in control failures.
Finally, preliminary tests demonstrated the potential effectiveness of vacuum treatment in a flexible structure (to produce an oxygen deficient atmosphere) for pest control and quality preservation of fresh and dried commodities.

Protecting grain without pesticides at the farm level in the tropics

S. Navarro, E. Donahaye, Miriam Rindner, A. Azrieli, and R. Dias
Three types of sealed structures for modified atmosphere of cereal grains stored in the open in tropical and subtropical climates was investigated. The advantage of the sealed storage lies in the generation of an oxygen-depleted and carbon dioxide enriched intergranular atmosphere of the storage ecosystem to arrest insect development. The three types of structures were: a) weld-mesh walled silos; b) frameless flexible envelopes (Volcani Cube); and c) a granary (GrainSafe). These are types of storages based on different logistic principles but having a common structural component, namely, a flexible liner.
A series of experiments carried out in Israel to develop the plastic structures included studies on permeability of plastic sheeting to oxygen and carbon dioxide, and resistance to insect and rodent penetration. Weld-mesh walled silos are suitable as medium-sized silos with a capacity of 60 to 1,000-tonnes. A circular bag of PVC contained within a vertical wall consisting of galvanized weld-mesh is used. The frameless flexible envelopes (Volcani Cube) consist for bag storage in small quantities of 10, 20 and 50 tonnes of cereal grains. The liner of PVC is made of an upper and a lower section which can be zipped together to form a gastight seal. The granary (GrainSafe) was designed to hold 540 kg nominal capacity of grain, consisting of a gastight cylindrical flexible plastic bag. The bag was inserted into a rigid white polypropylene board curved into a cylinder that forms a sheath surrounding the vertical sides of the flexible bag. Trials conducted with all three types of structures described in this paper in tropical and subtropical climates showed that sealed storage protected grain by maintaining the number of live insects below the threshold of economic damage without the need for pesticides.

Use of vacuum for quality preservation and insect control Ð demonstration trials II Ð Vacuum treatments of lemons and nectarines

Shlomo Navarro
INTRODUCTION
The vacuum treatment in the demonstration trial in Foxboro reported elsewhere indicated the feasibility of applying vacuum in a plastic structure where the enclosure takes the shape of contained commodity such as the Volcani cube.
The influence of low oxygen atmospheres on Plodia interpunctella and Amyelois transitella was demonstrated by Sodestrom et al., (1986) and on the codling moth, Cydia pomonella by Sodestrom et al., (1990; 1996). P. interpunctella is a cosmopolitan storage pest of many commodities and A. transitella is a common field and storage pest of almonds, pistachios and walnuts. C. pomonella is a quarantine pest of walnuts. It is common in North America but does not occur in Japan.
Responses of codling moth to oxygen deficient atmospheres have shown that diapausing larvae required an exposure time about 4 times that of nondiapausing larvae at 25°C (Sodestrom et al., 1990). However, for some agricultural commodities like walnuts, pre-shipment treatments may be scheduled to applications that are based on extended exposure times.
The possibility of applying vacuum treatment in the cube for controlling quarantine pests for fresh commodities like lemons and nectarines was also considered. Although long term storage of citrus is not recommended, extensive research has been undertaken in an attempt to establish the optimum temperature and atmospheric concentrations required to extend their storage life.
Ke and Kader (1990) showed that Valencia oranges can be treated with 0.5%, 0.25% or 0.02% oxygen at 5° or 10°C for up to 20 days without detrimental effects on their appearance or nutritional value. For lemons and nectarines also it would be necessary to determine which of the treatments might be officially approved. With the objective preliminary quality tests using lemons and nectarines responses to vacuum were tested.
Materials and Methods
Lemons and nectarines were from the 1999 harvest supplied by the Postharvest Quality and Plant Genetics and Commodity Protection Laboratories, respectively at the HCRL. A desiccator of 2.6 L capacity connected to a vacuum pump was used to create low pressure atmospheres of ~27-30Ó. All tests were carried out at room temperature (~25°C).
After 48 h treatment lemons were kept at 5°C for 14 days and then at room temperature for one day. Quality tests were carried out by examining the lemons externally and then internally, by cutting the fruits through the center.
Nectarine quality tests were carried out after vacuum treatment for 48 h at 25°C and storage for 6 days at normal atmosphere at 5°C. Nectarine quality was evaluated by cutting the fruits into two equal parts and examining the color change to the inner sections. Also a sheer press test was used to determine the firmness of the fruit to compare it after treatment with the control.
Results and Discussion Lemons exposed to vacuum conditions for 48 h at ~ 25°C did not reveal any apparent difference from the control. However, on a personal communication with Luis Aung (Post-harvest Quality and Plant Genetics, ARS, HCRL, Fresno), the complex situation of lemon response to modified atmospheres was clarified. Therefore, it is suggested that these promising preliminary results be considered very carefully and further detailed tests be carried out for durability of lemons to modified atmosphere treatments.
Two tests of nectarines exposed to vacuum were carried out. The firmness test resulted in 3.5 kg/cm² for nectarines exposed to vacuum and 1.4 kg/cm² for the control. In the second test the pressure in the exposure chamber increased to 25-27Ó Hg and the vacuum treatment did not differ from the control. In addition the firmness level for both was 1.8 kg/cm². Visual inspection inside the nectarines revealed a slight darkening band around the stone covering an area of about 20% of the meat. From these preliminary observations it was deducted that nectarines are highly sensitive fruits to vacuum and that a more in depth work would be necessary to reveal the value of vacuum at different temperatures.
For fruits that are able to tolerate vacuum conditions, it is suggested that further tests are carried out under controlled conditions for each specific quarantine insect pest. However, more promising is the potential of vacuum treatment for dried fruits and nuts, because these commodities are better preserved under low oxygen conditions. Vacuum treatment in cubes, for commodities where exposure time does not pose a significant limitation, appears to be a promising alternative to methyl bromide.
References
Aung L. (1999) Personal communication. Post-harvest Quality and Plant Genetics, USDA, ARS, HCRL, Fresno.
Ke, D. and Kader, A. (1990) Tolerance of ÒValenciaÓ oranges to controlled atmospheres as determined by physiological responses and quality attributes. J. Amer. Soc. Hort. Sci. 115 (5): 779-783.
Soderstrom, E.L. and Brandl, D. (1984) Low-oxygen atmosphere for postharvest insect control in bulk-stored raisins. J. Econ. Entomol. 77:440-445.
Soderstrom, E.L., Brandl, D. and Mackey, B.E. (1990) Responses of codling moth (Lepidoptera: Torticidae) life stages to high carbon dioxide or low oxygen atmospheres. J. Econ. Entomol. 83: 472-475.
Soderstrom, E.L., Brandl, D. and Mackey, B.E. (1996) High temperature and controlled atmosphere treatment of codling moth (Lepidoptera: Torticidae) infested walnuts using a gas-tight treatment chamber. J. Econ. Entomol. 89(3): 712-714.
Soderstrom, E.L., Mackey, B.E. and Brandl, D. (1986) Interactive effects of low-oxygen atmospheres, relative humidity, and temperature on mortality of two stored-product moths (Lepidoptera: Pyralidae). J. Econ. Entomol. 79: 1303-1306.

Storage of dried fruits under controlled atmospheres for quality preservation and control of nitidulid beetles

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli
Among the important pests of dried fruits are nitidulid beetles. Infestation starts in the field and unless control measures are employed, they and other pests continue to multiply and develop during storage. Methyl bromide has been used for fumigating dried fruits. However, because it is associated with the depletion of the atmospheric ozone, action has been taken to phase out its use in agriculture. This work was undertaken to develop a controlled atmosphere treatment which would remove insects from the dried fruit, prevent insect development and preserve fruit quality. Dates grown in Israel served as a model for development of the technology. A controlled atmosphere of 60-80% carbon dioxide was used within a 151 m³ plastic chamber partially filled with 30 tons of dates stacked in crates on pallets. At the initial purge phase the desired carbon dioxide concentration was obtained in the chamber within one hour by introducing the gas under high pressure. An intermittent maintenance phase was then applied for 4.5 months using approximately 0.8 kg carbon dioxide per day. At the end of storage, quality of the treated dates was compared to controls stored at -18°C. No significant difference was found between the treated dates and controls. The insect population was effectively controlled. This technology is proposed for the treatment of stored dried figs to control pests and maintain quality.

Application of vacuum in a transportable system for insect control

S. Navarro, E. Donahaye, R. Dias, A. Azrieli, Miriam Rindner T. Phillips, R. Noyes, P. Villers, T. deBruin, R. Truby and R. Rodriguez
It was demonstrated that the response of insects to low pressures is temperature and moisture dependent. At 25°C and 65% relative humidity complete mortality of adults was obtained within 7 h when exposed to 20 mm Hg. Trogoderma granarium larvae were the most resistant species, for which under the same conditions, a 120-h exposure was necessary. To control the quiescent T. granarium larvae within a 72-h exposure time it was necessary to increase the temperature to 30°C.
These encouraging reports led to the idea of developing a transportable system to render the technology a practical tool for the control of insect pests. Two sets of experiments were carried out using a 15 m³ capacity plastic container termed the Volcani Cube. This container is made of a flexible liner and characterized by its transportability. The first test was carried out in Foxboro MA, USA using an oil-lubricated vacuum pump (3 hp) to reduce the pressure to 25-mm Hg within 25 min. Then the pressure was maintained between 25 to 29 mm Hg for 17 days. Three sets of bioassay replicates were retrieved on day 3, 10, and 17 of treatment. Complete mortality of test insects was observed on the 3-days exposure to vacuum. The second test of vacuum was carried out in Israel using a similar set up for the vacuum pump and the Volcani Cube. The purpose of the tests was to study the technology that would contribute to improved performance. Vacuum was maintained within 22 and 75 mm Hg for over 25 days.

Critical Limits of sealing for successful application of Controlled Atmosphere or Fumigation

S. Navarro and L. Zettler
A fundamental requirement for the successful application of gaseous treatments to control stored-product insects is a well-sealed structure. A flexible fumigation structure of 7.5m³ capacity that is used for outdoor storage of stacked commodities was used to demonstrate the critical limits of the degree of sealing using the variable pressure test. Time in minutes for the half-life pressure decay was correlated with daily ventilation rates of O₂, CO₂, phosphine and methyl bromide. The ventilation rates were tested using different sizes of cross section leak areas with orifices of 1.6 mm, 3.2 mm and 6.4 mm i.d. To evaluate the influence of temperature on the rate of gas exchange, the cube was tested when it was under cover by providing shading to minimize the direct solar heating effect, and when it was exposed to direct solar heating.
Oxygen infiltration rate for modified atmospheres was 0.5 O₂%/day at 5 min half-life pressure decay when the chamber was under shade. For the same level of gastightness, gas loss was 0.8 O₂%/day when exposed. CO₂ loss rate was 2%/day at 5 min half-life pressure decay when the cube was under shade and 3%/day when the cube was exposed. Loss rate of phosphine from the cube for the shaded conditions was 100 ppm/day at a 3-min half-life pressure decay time. A sealing equivalent to 4.5 min half-life pressure decay time was required when exposed. The methyl bromide loss rate of 1.0 g/m³/day was equivalent to about 5 min half-life pressure decay time. At the time tests were carried out with methyl bromide, ambient temperature differences were not large enough to show different loss rates between the shaded and the exposed cube.

Insect control using vacuum or CO₂ in transportable flexible liners

S. Navarro, E. Donahaye, R. Dias Miriam Rindner and A. Azrieli
Although there is a large number of suggested potential alternatives to MB for disinfestation of durable commodities, development of most of these alternatives is likely to be costly. The combined factors of MB phase-out, the gradual development of insect resistance to fumigants and the undesirable effects of fumigant residues in food, have led to the idea of using controlled atmospheres. The objective of this investigation was to develop an alternative control treatment based on vacuum or a combination of heat and CO₂.
Response of insects to low pressures is temperature and moisture dependent. It was demonstrated that at 25°C and 65% relative humidity complete mortality of adults of most common storage insect pests was obtained within 7 h when exposed to 20 mm Hg. Use of vacuum in rigid structures requires robust and expensive treatment chambers that limit its application. It has been economically justified only for special treatments, such as in the case of fumigation under vacuum for quarantine treatments. The use of increased CO₂ concentrations has also been identified as effective in the control of storage insects using the flexible liners. However, its application depends on the availability of CO₂ particularly in production areas. Our experience demonstrates that accessibility to power needed to operate a vacuum pump poses an advantage over the use of CO₂.
These encouraging reports led to the idea of developing a transportable system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15 m3 capacity plastic container termed the Volcani Cube. This container is made of a flexible liner and characterized by its transportability. An oil-lubricated vacuum pump (3 hp) to reduce the pressure to 25-mm Hg within 25 min was used. The purpose of the tests was to study the technology that would contribute to improved performance. The possibility of maintaining low pressures within 22 and 75 mm Hg in the Volcani Cube over extended periods of several months was successfully tested.

Studies on the effect of alterations in pressure and composition of atmospheric gases on the Tropical Warehouse moth Ephestia cautella (Walker), as a model for stored-product insects

Shlomo Navarro
The influence of changes in pressure and atmospheric gas composition on stored-product insects were investigated by examining various reactions of the tropical warehouse moth Ephestia cautella (Walker). Moth pupae, 0-24 hr, old. were exposed to different concentrations of oxygen, and carbon dioxide and to different low pressures, at different combinations of air relative humidity at a temperature of 26±1°C. Adult emergence, loss in weight, rate of respiration, and some biochemical aspects were examined. The findings show that:

At an oxygen concentration of 3.2% or a carbon dioxide concentration of 20.7%, exposure for 6 days resulted in loss in weight by the pupae of 27.3% and 44.1% respectively, when the ambient relative humidity was 55%. Under these conditions complete pupal mortality was recorded. However, under the same gas concentrations, but when the air relative humidity was high, loss in weight was low and the pupae were able to survive.

Calculations carried out to determine critical threshold values for loss in weight causing pupal mortality, show that under conditions of low oxygen tension at different combinations of relative humidity these values range between 17.1 and 24.6%. Similarly, this critical threshold value for pupae exposed to different relative humidities is situated over a range of 17.9 to 19.8%.

Under the influence of a 1.3% concentration of oxygen or carbon dioxide concentration higher than 50.5%, high mortalities were recorded in spite of the extremely small loss in weight of the pupae when the relative humidity was 95%.

Respiration curves obtained from pupae subjected to normal atmospheric conditions (daily measurements of oxygen consumption were 0.398 - 0.797 microliter/mg/hr. and carbon dioxide production were 0.330 - 0.747 microliter/mg/hr.), were characteristic U-shaped.
At low oxygen concentrations (4.98 - 5.21%) these curves lose their characteristic shape and tend to straighten out. This is accompanied by a significant lowering in rate of respiration values to averages of 0.428 microliter oxygen/mg/hr., and 0.314 microliter carbon dioxide/mg/hr. At the lowest oxygen concentration of 1. 3% the pupal respiration rate decreases progressively with pupal age.
For all the treatments, respiration rates at the low relative humidity are higher than those at the high relative humidity, except for exposure at the lowest oxygen concentration tested (1.3%).

Carbon dioxide at a concentration of 4.9% resulted in a certain acceleration, though not a significant one, in the rate of pupal respiration, whereas an increase in concentration to 20.3 - 20.7% was expressed by a reduction in rate of respiration with a tendency to flattening of the pupal respiration curve.
At the high carbon dioxide concentration (88.1 to 89.2%) the shape of the respiration curves is characterized by a progressive reduction in the rate of respiration with exposure time.
With the exception of the high carbon dioxide concentration (88.1-89.2%) respiration rate was higher at the low relative humidity tested (20%).

Respiratory quotient values obtained under the influence of low oxygen tension, and in the presence of different concentrations of carbon dioxide, were higher in the treatments that resulted in progressive reduction in respiration rate during exposure (1.3% for oxygen, and 88.1-89.2% for carbon dioxide). Respiratory quotients were also higher under the influence of the higher relative humidity

A model was formulated to demonstrate the influence of extreme conditions of oxygen deficit, and high carbon dioxide concentrations at different relative humidities, that produce 95% pupal mortality. These curves enable one to indicate combinations of environmental conditions liable to be lethal to insects.

In experiments carried out at low pressures it was found that even at an absolute air pressure of 200 mm Hg considerable pupal mortality occurred when the relative humidity was low (18.4%).
From comparison of results obtained at low pressures and at atmospheric pressures it was found that pupal response was the same at the same partial pressures of oxygen and water vapor. Thus it was found that in spite of the low absolute total pressure of 48 mm Hg to which the test insects were exposed, mortality was not recorded so long as the partial pressure of oxygen corresponded to 2.9% at normal atmospheric pressure, and high relative humidity (100%).

The loss in pupal weight reached 32.6% within 48 hr. when the insects were exposed to an absolute pressure of 100 mm Hg. and a gas composition of normal air (partial pressures of oxygen and water vapor corresponding to 2.8% and 9.3% respectively at atmospheric pressure). However, at the same absolute pressure (100 mm Hg) when the partial pressure of oxygen corresponded to 12.9% at atmospheric pressure, the loss in pupal weight within 48 hr was only 7.6%, which did not result in insect mortality.

It was also found that at low pressure there is a significant correlation between loss in pupal weight and survival. Calculation of the critical value shows that at a pressure of 100 mm Hg. when the pupae are exposed to different relative humidities, they are unable to survive after their loss in weight rises above 17.6%.

Respiration rates of pupae at low pressures reveals the primary role of the partial pressure of oxygen in the level of respiration rate as expressed by oxygen consumption and carbon dioxide production.

From comparison of the results between the influence of low pressures and at atmospheric pressure when the partial pressures of oxygen and water vapor were different from those of the air, it can be deduced that the partial pressure of oxygen has a decisive effect on the test insect, while no significant function can be attributed to the low pressure itself under these experimental conditions.

Following a 24 hr exposure to the different gas concentrations ~~ the mean content of triglycerides of the body of the pupae was found to be 20.85%, while after an additional 24 hr exposure the triglycerides level dropped to an average of 17.09%.. This difference is significant. However, no significant difference could be attributed to the effect of the relative humidities tested at different oxygen and carbon dioxide concentrations.

The concentration of some glycolysis intermediates in the hemolymph of pupae was determined. Under the effect of 1.02% oxygen, lactic acid increased from 6.1 mg/100 ml in the control group to 287.9 mg/100ml. Under the same conditions pyruvic acid concentration increased from 3.8 mg/100 ml. in the control group to 7.5 mg/100 ml. Carbon dioxide at 88.8% caused a significant increase of lactic acid to the level of 74.2 mg/100 ml.
The alpha glycerophosphate level increased from 17.17 mg/100 ml. in the control group to 33.53 mg/100 ml under the effect of 1.18% oxygen. Under the same concentration the glycerol level increased from 7.26 mg/100 ml in the control group to 16.60 mg/ 100 ml. Alpha glycerophosphate and glycerol concentrations increased significantly at 89.43% carbon dioxide, resulting in 33.19 mg/ 100 ml and 19.02 mg/100 ml respectively. The significance of these changes in the concentration of glycolysis intermediates is discussed.

The effect of oxygen and carbon dioxide gradients on the vertical dispersion of grain insects in wheat

S. Navarro, T. G. Amos and P.Williams
A study was made on the dispersion of 0 14 day old adult Oryzaephilus surinamensis (L.), Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) at 25°C in vertical columns of wheat (m.c. 12.1%,) l00cm tall. When the columns contained ordinary air, O. surinamensis dispersed from top to bottom within 24 hr whereas S. oryzae and R. dominica penetrated to a depth of only 50 cm in 72 hr. When controlled gas gradients were imposed on the columns from the bottom, the concentration of O₂ in one series of experiments ranged from 0.9% at the bottom to 18.5% at the top whilst in another series that of CO₂ ranged from 70.5% to 3.3%. In both gas gradients the downward dispersion of 0. surinamensis was restricted but the distribution of the other two insect species was unaffected because they did not penetrate deep enough to encounter unfavorable concentrations.

Response of adults of the grain mite, Acarus siro L. To modified atmospheres

S. Navarro, O. Lider, and U. Gerson
Mortality of newly emerged adults of Acarus siro L. was assayed by exposing them to 2, 4, 6, 10, 21% O₂ in N₂, to 10, 20, 30 40% CO₂ in 21% O₂ and with the balance of the atmosphere made up of N₂. Tests were conducted at 75% relative humidity and 15 or 26°C in a specially designed apparatus. Mean duration of mite survival in air was 11 and 7 d at 15 and 26°C, respectively. Exposure to 2% O₂ was required to obtain 100% mortality with 72 h at 15°C; the same result was obtained within 120 h at 26°C by exposure to 10% O₂. At 15°C, 30% CO₂ was required for 96 h to achieve 100% mortality; at 26°C, 20% CO₂ or above produced the same result within 72 h.

Exposure of Ephestia cautella (Wlk.) (Lepidoptera, Phycitidae) to Low Pressures: Effects on Adults

S. Navarro and M. Calderon
Adults of Ephestia cautella (Wlk.) were exposed to pressures of 100, 200, 300, 400 and 760 mm Hg at 26 ± 1°C: and 70 ± 5% r.h., in a specially designed apparatus in which a controlled atmospheric gas composition was maintained. Adult life was shortened at all reduced pressures; at 100 mm Hg all adults died in 14 hr. Oviposition was affected at reduced pressures resulting in a significant reduction in the number of eggs laid. At 100 mm Hg oviposition was negligible. A hypothesis to explain these observations is mentioned.

Exposure of Ephestia cautella (Wlk.) pupae to carbon dioxide concentrations at different relative humidities: the effect on adult emergence and loss in weight

S. Navarro and M. Calderon
The effects on mortality and loss in weight caused by 21, 51 and 88% carbon dioxide in combination with relative humidities of 20-22, 54-55, and 95-96 % were tested on 0-24 hr old Ephestia cautella pupae, at 26°C. Exposure times ranged from I to 6 days. At 54-55 %, and 20-22 % r.h. pupal mortality was high for all carbon dioxide concentrations used, while at 95 % r.h. total mortality was obtained only at the highest carbon dioxide concentration tested. At carbon dioxide concentrations of 51 and 88 % a 9-11% concentration of oxygen was present. At 20-22 % and 54-55 % r.h. 1oss in weight of pupae exposed to carbon dioxide concentrations of 21% and higher was very pronounced. At 95-96% r.h, none of the treatments resulted in loss in weight exceeding 16% after six days of exposure. A 95% mortality curve represents the interrelated effect of carbon dioxide and relative humidity on the moth pupae. The fumigant effect of carbon dioxide is discussed.

Integration of controlled atmosphere and low temperature for disinfestation and control of dried fruit beetles

Shlomo Navarro, Ezra Donahaye, Miriam Rindner, Raphael Dias and Avi Azr1eli
Nitidulid beetles are important pests of dried fruits, particularly dates at the time of harvest. Upon arrival at the packing stations, dates are disinfested by fumigation. This treatment serves a twofold purpose of stimulating the active insect stages (larvae and adults) of field infestations to abandon the fruits and also killing all stages of the insect population. Experiments were carried out to investigate the effect of various modified atmospheres (MAs) and low pressures alone in prompting the emigration of Nitidulid beetles from infested dried fruit, for which dates served as a model. The most effective treatments were pressure of 100 mm mercury (Hg) and 2.8% oxygen (02) in air, both of which caused over 80% of the initial insect populations to emigrate from the fruit after a 4-hr exposure. However, the MA treatments required longer exposure times to achieve complete mortality as compared with standard fumigation procedure. An alternative approach to controlling the insects after disinfestation by MAs was by storage at low temperatures. Exposure to -5°C caused relatively slow kill. Pupae were the most resistant stage, necessitating approximately 90 hr to produce 99% kill (LT99) of Carpophilus mutilatus Er and Carpophilus hemipterus L. Exposure to -18°C caused very rapid kill of both species, LT99 of all stages being obtained within 2.25 hr.

Protecting Grain Without Pesticides at the Farm Level in the Tropics

S. Navarro, E. Donahaye, M. Rindner, A. Azrieli and R. Dias
Three types of sealed structures for modified atmosphere storage of cereal grains stored in the open in tropical and subtropical climates were investigated. The advantage of sealed storage lies in the generation of an oxygen depleted and carbon dioxide-enriched inter-granular atmosphere of the storage ecosystem to arrest insect development. The three types of structures assessed were: (a) weldmesh-walled silos, (b) frameless flexible envelopes (Volcani Cubes); and (c) a sealed granary (GrainSafe). These structures are based on different logistic principles but have a common structural component, namely, a flexible liner.
A series of experiments carried out in Israel to develop the plastic structures included studies on the permeability of plastic sheeting to oxygen and carbon dioxide, and resistance to insect and rodent penetration. Weldmesh-walled silos are suitable as medium-sized silos with a capacity of 60-1,000 t. A circular bag of plastic liner contained within a vertical wall consisting of galvanized weldmesh is used. The frameless flexible envelopes (Volcani Cubes) are designed for bag storage of small quantities (10, 20 and 50 t) of cereal grains. The plastic liner is made of an upper and a lower section which can be zipped together to form a gastight seal. The granary (GrainSafe) was designed to hold 540 kg nominal capacity of grain, and consists of a gastight cylindrical flexible plastic bag. The bag is inserted into a rigid white polypropylene board curved into a cylinder that forms a sheath surrounding the vertical sides of the flexible bag. Trials conducted with all three types of structures described in this paper in tropical and subtropical climates showed that sealed storage protected grain by maintaining the number of live insects below the threshold of economic damage without the need for pesticides.

The effects of low oxygen tensions on three stored-product insect pests

S. Navarro
The relationship between different oxygen tensions and exposure times producing 95% mortality, and loss in weight of three stored-product insects at 54% R.H. and 26°C, was determined. Ephestia cautella (Wlk.) pupae and Tribolium castaneum (Herbst) adults reacted in a similar pattern: the lower the oxygen concentration, the shorter the exposure time needed to produce 95% mortality, and the higher the rate of loss in weight. The response of Sitophilus oryzae (L.) adults was different: there was greater sensitivity at 1% oxygen than at the lower or higher levels of oxygen tested.
A relationship was demonstrated between low oxygen tensions (0-5%) and the relative humidity of the environment for producing a lethal atmosphere for E. cautella pupae and T. castaneum adults.

Application of modified atmospheres for controlling stored grain insects

S. Navarro and E. G. Jay
Modified atmospheres (MAs) were investigated as a substitute for conventional stored grain insect control methods, The response of the four developmental stages of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium castaneum (Herbst) to different MAs at temperatures from 15 to 32°C was studied. The pupae of all three species, plus the larvae of S. oryzae, were less susceptible than eggs and adults to the tested MAs. Exposure to 60 % CO₂ in air for 120 h at 27°C was sufficient to cause 100% mortality of all stages of O. surinamensis, but not of S. oryzae or T. castaneum.
A field trial was conducted to determine the feasibility of the method in a bin containing 6,881 tonnes of wheat, and the effect of the treatment on a natural population of stored product insects was studied. Mortality was correlated with the location of the insects in regard to temperature and movement of the CO₂ front from the bottom to the top of the treated bin.

Recirculation rate requirements for adequate distribution of carbon dioxide in grain silos.

Navarro, S., Jay, E.G., and Leesch, J.G.
A 665.7 L experimental bin containing wheat and equipped with a recirculation system was used to determine the relationship between the time needed to attain uniform distribution of carbon dioxide (CO₂) and the recirculation rate. A cyclic pressure increase and decrease was observed which was caused by the adsorption and desorption processes taking place during gas recirculation in the bin. An index based on the ratio of lowest to highest concentration of CO₂ at a given time was used to determine the distribution of the CO₂. An equation based on this index is proposed as a means of predicting the time needed to attain uniform distribution based upon the recirculation rates used.
Effect of modified atmospheres on microflora and respiration of California prunes

Zettler, J.L. and Navarro, S.
We investigated the possibility that California prunes stored in modified atmospheres (MAs) will tolerate higher water activity (a_w) levels than those required at normal atmospheres and that the naturally occurring microfloral infection level on the prunes may generate the MAs that inhibit mold activity in airtight conditions. Dry prunes were moisturized to a range from 16 to 38% moisture content (m.c.) to acquire samples with 0.575 to 0.858 a_w. In unsealed conditions at 35°C, there was a level of naturally occurring microorganisms (aerobic plate count, yeast and mold count) that generally increased above 0.70 a_w. However, incubating these samples in a sealed container for 35 days at 35°C indicated that levels of naturally occurring microorganisms remained unchanged throughout the range of water activities. Microfloral respiration as a function of temperature was determined by incubating similarly moisturized prune samples at 25, 30 and 35°C and then measuring the declining O₂ concentrations through time. Results showed that the higher both the water activity and temperature, the more intense the O2 consumption by the product. A nearly linear relationship was observed between O₂ depletion and time. Anaerobic conditions were reached in less than 2 days at 25°C and 0.858 a_w, the highest water activity tested. At higher temperatures, anaerobic conditions were achieved at water activities of 0.824 and above. These results indicate that under aerobic conditions microorganisms can flourish on and cause deterioration of prunes if the water activity of the fruit is above 0.7 (m.c. of 24.6%). However, under sealed conditions, prunes can tolerate a higher water activity without microorganism growth or deterioration of the fruit.

Storage of dates under carbon dioxide atmosphere for quality preservation

Navarro, S., Donahaye, E.J., Miriam Rindner and Azrieli, A.
Dates grown in Israel served as a model to demonstrate the feasibility of storing dried fruit under CO₂ atmosphere. A controlled atmosphere of 60-80% CO₂was used within a 151 m3 plastic chamber partially filled with 30 tonnes of dates stacked in crates on pallets. The dates were stored in the chamber in bulk (in boxes of 10 kg or crates of 400 kg on pallets) or packed (250 g capped plastic cups) on pallets containing dates of vars. 'Hallawi', 'Hadrawi', 'Zahidi', 'Derei' and 'Ameri'. Dates were sampled before closing the chamber, after one month and after 4.5 months at the end of storage. The following were investigated: presence of insects and molds; skin sloughing; sugar formation; water activity (aw); and color changes (only on var. Zahidi). At the initial purge phase the desired CO₂ concentration was obtained in the chamber within one hour by introducing the gas under high pressure. An intermittent maintenance phase was then applied for 4.5 months using approximately 0.8 kg CO₂ per day. At the end of storage, quality of the treated dates was compared to controls stored at -18°C. No significant difference was found between the treated dates and controls. The insect population was effectively controlled. This technology is proposed for the treatment of stored dates to control pests and maintain quality.

Enhanced effectiveness of vacuum or CO₂ in combination with increased temperatures for control of storage insects

Navarro S., Finkelman S., Sabio G., Isikber A., Dias R., Miriam Rindner, and Azrieli A.
Laboratory studies were carried out to identify the combinations that enhance the effectiveness of insect control based on vacuum or CO₂ in combination with increased temperatures as quarantine treatment of storage pests. The role of the commodity moisture content and the partial pressure of oxygen on the effectiveness of vacuum were described. Adults of Lasioderma serricorne were exposed to low pressures at 30°C, for which LT99 value was 15 h when exposed to 25 mm Hg. Diapausing larvae of Trogoderma granarium were most resistant species, whereby 172 h exposure was necessary under the same conditions. Effect of CO₂ at 45°C on reducing the exposure time for diapausing larvae of T. granarium showed that by increasing the CO₂ concentration to 90% the LT99 value decreased to about 10 h, whereas at 35°C the LT99 value was 29 h. Ephestia cautella larvae were shown to be the most resistant stage to 90% CO₂ at 40°C, with an LT99 value of only 6 h. For Oryzaephilus surinamensis under the same conditions, the LT99 value was 9 h for the most resistant egg stage. These encouraging results led to the idea of developing a transportable flexible storage system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15-m3 capacity plastic container termed the ÒVolcani CubeÓ or ÒGrainPro CocoonÓ. Bioassay in field trials at 30°C demonstrated that complete mortality of test insects composed of all four developmental stages of E. cautella and Tribolium castaneum was observed upon 3-days exposure to vacuum maintained within 22 and 75 mm Hg.

Quarantine treatment of storage insect pests under vacuum or CO₂ in transportable systems.

S. Navarro, S. Finkelman, G. Sabio, A. Isikber, R. Dias, M. Rindner And A. Azrieli
The objective of our investigation was to identify the combinations that enhance the effectiveness of insect control based on vacuum or CO₂ in combination with increased temperatures as quarantine treatment of storage pests. In laboratory studies with Lasioderma serricorne exposed to low pressures at 30°C, LT99 value for adults was 15 h when exposed to 25 mm Hg. Trogoderma granarium diapausing larvae were most resistant species, whereby 172 h exposure was necessary under the same conditions. Effect of CO₂ at 45°C on reducing the exposure time for diapausing larvae of T. granarium showed that by increasing the CO₂ concentration to 90% the LT99 value decreased to about 10 h, whereas at 35°C the LT99 value was 29 h. Ephestia cautella larvae were shown to be the most resistant stage to 90% CO₂ at 40°C, with an LT99 value of only 6 h. For Oryzaephilus surinamensis under the same conditions, the LT99 value was 9 h for the most resistant egg stage. These encouraging reports led to the idea of developing a transportable flexible storage system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15-m3 capacity plastic container termed the ÒVolcani CubeÓ or ÒGrainPro CocoonÓ. Bioassay in field trials demonstrated that complete mortality of test insects composed of all four developmental stages of E. cautella and Tribolium castaneum was observed when exposure to a vacuum for 3-days.

Integrated storage pest control methods using vacuum or CO₂ in transportable systems.

Navarro S., Finkelman S., Donahaye E., Dias R., Miriam Rindner and Azrieli A.
The suggested potential alternatives to MB (methyl bromide) for disinfestation of durable commodities are likely to be costly compared to the use of MB. In addition very few of the suggested treatments have the effectiveness of short exposure time comparable to MB. The objective of our investigation was to identify the combinations that enhance the effectiveness of the treatments based on vacuum or a combination of heat and CO₂.
The influence of CO₂ at 45°C on reducing the exposure time expressed as LT99 values for diapausing larvae of Trogoderma granarium showed that by increasing the CO₂ concentration to 90% the exposure time decreased to about 9.5 h, whereas at 35°C the LT99 value was 29.1 h. Tests with Ephestia cautella showed that the pupae was the most resistant stage to the same treatment with an LT99 value of only 3.4 h, and for Oryzaephilus surinamensis under the same conditions it was less than 2 h for the most resistant larval stage. Laboratory studies with Lasioderma serricorne exposed to low pressures at 30°C, LT99 values for adults was 15.3 h when exposed to 25 mm Hg. Trogoderma granarium larvae were the most resistant species, for which under the same conditions 172 h exposure was necessary. These encouraging reports led to the idea of developing a transportable system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15-m3 capacity plastic container termed the ÒVolcani CubeÓ or ÒGrainPro CocoonÓ. The pressure was maintained between 25 to 29 mm Hg for 17 days. Bioassay in field trials demonstrated that complete mortality of test insects composed of mixed ages of E. cautella Plodia interpunctella, and larvae of T. castaneum was observed on the 3-days exposure to vacuum.

Laboratory and field tests on vacuum or CO₂ for the control of storage insects.

Navarro S., Finkelman S., Donahaye E., Miriam Rindner, Dias R., Azrieli A.
The suggested potential alternatives to MB (methyl bromide) for disinfestation of durable commodities are likely to be costly compared to the use of MB. In addition, very few of the suggested treatments have the effectiveness of short exposure time comparable to MB. The objective of our investigation was to identify the combinations that enhance the effectiveness of the treatments based on vacuum or a combination of heat and CO₂.
The influence of CO₂ at 45°C on reducing the exposure time expressed as LT99 values for diapausing larvae of Trogoderma granarium showed that by increasing the CO₂ concentration to 90% the exposure time decreased to about 9.5 h. For the same species at 35°C the LT99 value was 29.1 h. To obtain LT99 values for diapausing larvae of Trogoderma granarium at 25 mm Hg and 35°C, 172-h exposure was necessary.
Tests with Ephestia cautella showed that the pupae was the most resistant stage to the treatment of 90% CO₂ at 35°C for which an LT99 value of 17 h was required. For pupae, the most resistant stage of Tribolium castaneum, the LT99 value was 25 h when exposed to 92% CO₂, and at 100 mm Hg the LT99 value was 45 h at 30°C. Oryzaephilus surinamensis exposed to 90% CO₂ required the LT99 value of 9 h for the eggs, most resistant stage at 35°C. Laboratory studies with Lasioderma serricorne exposed to low pressures at 30°C, LT99 values for adults was 15.3 h when exposed to 25 mm Hg.
These encouraging reports led to the idea of developing a transportable system to render the technology a practical tool for the control of insect pests. Experiments were carried out using a 15-m3 capacity plastic container termed the ÒVolcani CubeÓ or ÒGrainPro CocoonÓ. The pressure was maintained between 25 to 29 mm Hg for 17 days. Bioassays in field trials were conducted with 7 tonnes of cocoa beans stored in the ÒVolcani CubeÓ. These trials demonstrated that complete mortality of test insects composed of mixed ages of E. cautella, and T. castaneum was observed on the 3-days exposure to low pressures maintained within the range of 25 and 75 mm Hg.
Seed Storage In The Tropics Under Gastight Sealed Conditions

Shlomo Navarro, Ezra Donahaye, Miriam Rindner, Avi Azrieli and Refael Dias
The viability of seeds stored in gastight sealed structures in the open, under modified atmospheres, in tropical and subtropical climates was investigated. The essential advantage of sealed storage lies in the generation of an oxygen-depleted and carbon dioxide enriched intergranular atmosphere of the storage ecosystem to arrest insect development. In addition, the sealed storage prevents ingress of moisture into the already dry seeds when the ambient humidity of the surrounding environment rises. The two types of structures investigated were: a) frameless flexible envelopes for bagged grain (Volcani Cubes) of 5 to 150 tonnes; and b) a granary (GrainSafe) to hold 540 kg of cereal grain.
Under tropical conditions, when grain is stored in the open with no shade, ambient diurnal temperature fluctuations, can create temperature gradients within the stack that cause convection currents to carry moisture to the upper layers of grain. In the granary a protective roof diminishes the effect of temperature gradients. However, to overcome this effect in the flexible envelopes, the use of a shade screen placed above the structure was investigated. This material described as a knitted thermal screen is formed from aluminum coated high-density polyethylene threads. Trials in Israel and the Philippines showed that the shade screens had a strong attenuating influence on temperature gradients. For dry paddy seeds, it was shown that after five months storage under a shade screen, no perceptible increase in moisture content was found at the top of the stack and the seeds remained in good condition. Under tropical climates this solution enables safe storage of maize and paddy seeds. Trials conducted with these two types of structures in tropical and subtropical climates showed that seeds are protected under sealed storage by maintaining the number of live insects below the threshold of economic damage without the need for pesticides.
Respiration of Rhyzopertha dominica (F.) at reduced oxygen concentrations

M. Emekci, S. Navarro, E. Donahaye, M. Rindner and A. Azrieli

Abstract:
Developmental stages of Rhyzopertha dominica were exposed to atmospheres containing 1%, 2%, 3%, 5%, 10% or 15% oxygen (O₂) in nitrogen at 30&Deg;C and 70% r.h. Respiration rates were determined with a gas chromatograph. The O₂ intake and carbon dioxide (CO₂) output by insects were expressed in µl/insectÊh or µl/mgÊh. Respiration of eggs, young and old larvae, pupae, and adults at normal atmospheric air were at rates of 0.0029, 0.41, 2.52, 0.82, and 2.86Êµl CO₂/insectÊh, respectively. Respiration rates of the same stages in terms of insect weight were 0.14, 4.83, 1.98, 0.64 and, 2.58Êµl CO2/mgÊh, respectively. At reduced O₂ levels respiration rates of eggs, larvae and pupae were proportional to the O₂ levels. Adult respiration rates were high at 3% and 5% O₂ levels almost reaching that of normal atmospheric air, and were 2.56 and 2.85Êµl CO₂/insectÊh, respectively. In adults, respiration quotient values for the same O₂ levels were higher than at normal atmospheric O₂ and were 1.5 and 1.02, respectively. Respiration of adults in normal air between 20&Deg;C and 35&Deg;C increased with temperature and gas values varied between 0.89 and 6.82Êµl CO₂/insectÊh, respectively, or 0.93 and 5.63Êµl O₂/insectÊh, respectively.
Respiration of Tribolium castaneum (Herbst) at reduced oxygen concentrations

M. Emekci, S. Navarro, E. Donahaye, M. Rindner and A. Azrieli

Abstract:
Adults, eggs, young and old larvae and pupae of Tribolium castaneum (Herbst) were exposed to atmospheres containing 1%, 2%, 3%, 5%, 10%, and 15% oxygen in nitrogen at 30&Deg;C and 70% r.h. Respiration rates were determined with a gas chromatograph. The oxygen intake and carbon dioxide output by insects were expressed in µl/insect/h or µl/mg/h.
Adults exposed to 21% oxygen required an initial acclimatization period of at least 5Êh, after which the respiration rate remained stable. Based on this finding, all the respiration measurements were carried out after an initial adaptation of insects to the respirometer conditions for 24Êh. Respiration of eggs, young and old larvae, pupae, and adults at 30&Deg;C in normal atmospheric air was at rates of 0.0121, 9.25, 8.45, 1.45, and 4.67Êµl CO₂/insect/h, respectively. Respiration rates of the same stages in terms of insect weight were 0.32, 29.08, 3.33, 0.59 and 2.37Êµl CO₂/mg insect/h, respectively. At reduced oxygen levels respiration rates of eggs, larvae and pupae were proportional to the oxygen levels. Adult respiration was higher for 3% and 5% oxygen than for normal atmospheric air with rates of 4.77 and 4.98Êµl CO₂/insect/h, respectively. In adults, RQ values for the same oxygen levels were also higher than for normal atmospheric oxygen and were 1.07 and 1.18, respectively.
Effectiveness of short exposures of propylene oxide alone and in combination with low pressure or carbon dioxide against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

S. Navarro, A. A. Isikber, S. Finkelman, M. Rindner, A. Azrieli and R. Dias

Abstract:
Toxicity of the fumigant propylene oxide (PPO) alone and in combination with low pressure (100 mm Hg) or 92% CO₂ to all life stages of Tribolium castaneum using short exposure times (4 and 8 h) at 30°C was studied. Results indicated that PPO was moderately toxic with Ct products ranging from 120 to 608 mg h/l required to obtain complete mortality of the different life stages. A marked difference in susceptibility between life stages was recorded. Eggs were the most sensitive with a LD₉₉ value of 30.1 mg/l for 4 h, whereas pupae were the most tolerant with a LD₉₉ value of 146.5 mg/l. It was shown that an increase in exposure time from 4 to 8Êh resulted in 23%, 42%, 48% and 47% reductions of LD₉₉ values for eggs, larvae, pupae and adults, respectively.
There was no or very limited mortality of all stages except the egg (53% to 62%), when exposed to either 100 mm Hg or 92% CO₂ for 4 h. However, when 100 mm Hg or 92% CO₂ were combined with PPO, the LD₅₀ and LD99_{values for PPO in all stages except the egg were significantly reduced. Combinations of PPO with 100Êmm Hg or 92% CO₂ produced equal reductions in the LD₉₉ value from 146.5 to about 22Êmg/l for the most tolerant pupal stage. Both combinations also produced significant reductions in the LD₉₉values for larvae and adults (6.3- to 6.6-fold) compared with those exposed to PPO alone. These results indicated that 100Êmm Hg and 92% CO₂ each had a synergistic effect on the toxicity of PPO to T. castaneum. The combination of PPO with vacuum or CO₂ can thus provide a potential alternative to methyl bromide.

Influence of Temperature on Toxicity of Propylene Oxide at Low Pressure Against Tribolium castaneum
A.A. Isikber, S. Navarro, S. Finkelman, M. Rindner and R. Dias

Abstract:

Toxicity of propylene oxide (PPO) at low pressure against the most common stored-product insect, Tribolium castaneum (Herbst), over a short exposure time, was tested at three different temperatures (16, 22 and 30°C).

Toxicities of PPO at 100 mm Hg were strongly inuenced by ambient temperature. LD₅₀ and LD₉₉ toxicities ranged from 4.7 to 28.9 mg l^-1 and from 10.5 to 72.6 mg l^-1 respectively, showing that susceptibility was positively correlated to the temperature. The LD₉₉ values for all life stages (except the larval stage) were signicantly lower at 30 than those at 16 and 22°C. However, the LD₉₉ values for all life stages (except the pupal stage) at 16 were not significantly different from those at 22°C. A concentration time (Ct) product of 291, 171 and 98 mg h/l was required to obtain complete mortality (99%) of T. castaneum at 16, 22 and 30°C, respectively. Thus, the efficacy of PPO at 100mm Hg to all life stages of T. castaneum also decreased as the temperature decreased from 30 to 16°C.

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SHLOMO NAVARRO

Shlomo Navarro

Shbmo Navarro, Jonathan E Donahaye, Filipinas M. Caliboso and Glory Sabio

Shlomo Navarro, Jonathan Donahaye, A. Guray Ferizli, Miriam Rindner and Avi Azrieli

Shlomo Navarro

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli

Shlomo Navarro, and Filipinas M. Caliboso

S. Navarro, J.E. Donahaye and S. Fishman

Shlomo Navarro and Ezra Donahaye

Shlomo Navarro, Ezra Donahaye and Hovav Talpaz

Shlomo Navarro, Andreas Varnava and Ezra Donahaye

S. Navarro, E. Donahaye, R. Diaz, Miriam Rindner and A. Azrieli

S. Navarro, R. Dias and E. Donahaye

Shlomo Navarro and Ezra Donahaye

Shlomo Navarro, Ezra Donahaye, Miriam R1ndner, Raphael Dias and Avi Azrieli

S. Navarro and E. Donahaye

S. Navarro, E. Donahaye, Y. Kashanchi, V. Pisarev and O. Bulbul

S. Navarro and E. Donahaye

S. Navarro, Filipinas M. Caliboso, Glory Sabio and E.J. Donahaye

s. Navarro, e. Donahaye, r. Dias a. Miriam rindner and azrieli

S. Navarro, E. Donahaye, Glory C. Sabio, Miriam Rindner, R. Dias and A. Azrieli

S. Navarro and L. Zettler

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli

S. Navarro, E. Donahaye and H. Talpaz

S. Navarro, E. Donahaye, R. Dias and E. Jay

S. Navarro, E. Donahaye, R. Kleinerman and H. Haham

S. Navarro, E. Donahaye, R. Dias and E. Jay

S. Navarro, Y. Slavetski, E. Donahaye, B. Jacobsen, M. Rindner and A. Azrieli

S. Navarro

S. Navarro and M. Calderon

S.NAVARRO, E.DONAHAYE and M.CALDERON

. Navarro and A. Friedlander

S. Navarro, E. Donahaye and M. Calderon

. Navarro and M. Calderon

S. Navarro, E. Donahaye and M. Calderon

S Navarro and E Donahaye

An In-Depth Overview of Grain Storage Technology Throughout the World - Published Collectively For the First Time

The Mechanics and Physics of Modern Grain Aeration Management

Of worldwide interest to those involved in production, handling, storage, and marketing of grain and oilseeds

Features

Contents

Shlomo Navarro

S. Navarro, E. Donahaye, Miriam Rindner, A. Azrieli, and R. Dias

Shlomo Navarro

S. Navarro, E. Donahaye, Miriam Rindner and A. Azrieli

S. Navarro, E. Donahaye, R. Dias, A. Azrieli, Miriam Rindner T. Phillips, R. Noyes, P. Villers, T. deBruin, R. Truby and R. Rodriguez

S. Navarro and L. Zettler

S. Navarro, E. Donahaye, R. Dias Miriam Rindner and A. Azrieli

Shlomo Navarro

S. Navarro, T. G. Amos and P.Williams

S. Navarro, O. Lider, and U. Gerson

S. Navarro and M. Calderon

S. Navarro and M. Calderon

Shlomo Navarro, Ezra Donahaye, Miriam Rindner, Raphael Dias and Avi Azr1eli

S. Navarro, E. Donahaye, M. Rindner, A. Azrieli and R. Dias

S. Navarro

S. Navarro and E. G. Jay

Navarro, S., Jay, E.G., and Leesch, J.G.

Zettler, J.L. and Navarro, S.

Navarro, S., Donahaye, E.J., Miriam Rindner and Azrieli, A.

Navarro S., Finkelman S., Sabio G., Isikber A., Dias R., Miriam Rindner, and Azrieli A.

S. Navarro, S. Finkelman, G. Sabio, A. Isikber, R. Dias, M. Rindner And A. Azrieli

Navarro S., Finkelman S., Donahaye E., Dias R., Miriam Rindner and Azrieli A.

Navarro S., Finkelman S., Donahaye E., Miriam Rindner, Dias R., Azrieli A.

Shlomo Navarro, Ezra Donahaye, Miriam Rindner, Avi Azrieli and Refael Dias

M. Emekci, S. Navarro, E. Donahaye, M. Rindner and A. Azrieli

M. Emekci, S. Navarro, E. Donahaye, M. Rindner and A. Azrieli

S. Navarro, A. A. Isikber, S. Finkelman, M. Rindner, A. Azrieli and R. Dias

A.A. Isikber, S. Navarro, S. Finkelman, M. Rindner and R. Dias