The use of portable systems to control insect pests by low pressures
Simcha Finkelman*, Shlomo Navarro, Miriam Rindner, Refael Dias, and Avi Azrieli
Department of Food Science, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
*Corresponding author e-mail: finkelman_simcha@hotmail.com
Abstract: The possibilities of using low pressure as a method to control insects have long been suggested and studied. Until now the ability to implement the full potential of this method has been limited, but in recent years flexible mobile chambers made of welded PVC liners have been introduced. Under vacuum, these chambers shrink over the periphery of the commodity and hold it fast. The system is sealed by an air-tight zipper and is able to retain a vacuum or different compositions of modified atmospheres. At the base of the chamber, an inlet and hosing enable connection to a vacuum pump that maintains the prerequisite low pressure. Previous laboratory studies have revealed the effect of 50 ± 5 mm Hg on six important stored-product pests: Trogoderma granarium (Everts), Lasioderma serricorne (F.), Oryzaephilus surinamensis (L.), Tribolium castaneum (Herbst) Ephestia cautella (Walker), and Plodia interpunctella (Hübner). At 30°C and a relative humidity of 55% the egg is the most resistant stage in all species, the times needed to obtain 99% mortality being 46 h, 91 h, 32 h, 22 h, 45 h, and 49 h respectively. Additional results indicated that at lower temperatures or at higher relative humidities, the times needed to achieve mortality were prolonged. Three parameters are most important in the determination of treatment time required for a given commodity. To control all pests, the range of insect species likely to infest the specific commodity must be drawn up. Treatment time must be based on the sensitivity of the most resistant stage of the most resistant species in this list, which is obtained from knowledge of previous infestations. However, no less important are temperature and the relative humidity in the chamber, both these parameters being determined by the condition of the commodity. Consequently, it is the temperature and moisture content of the commodity, and its insect fauna that determine the duration of treatment. To demonstrate this principle, a range of commodities containing natural and artificial infestations was subjected to low pressure for 5 days exposure, under ambient conditions (Mediterranean summer climatic) and 100% mortality was recorded in all cases. In conclusion, the use of low pressure is now a promising option for insect control in stored commodities without the requirement of potentially harmful chemicals.
Key words: vacuum, flexible treatment chambers, stored-products, insects
