Modified Atmospheres for the Control of Stored-Product Insects and Mites
Shlomo Navarro
Department of Food Science, Agricultural Research Organization, Bet Dagan, Israel
Overview: Background and History Increased public concern over the adverse effects of pesticide residues in food and the environment has led to the partial replacement of fumigation by alternative control methods. Among these methods, the only one that retains the special capacity of fumigation for in-situ treatment of stored commodities, as well as offering a similar diversity of application technologies, is the modified atmosphere (MA) method. Modified or controlled atmospheres offer a safe and environmentally benign alternative to the use of conventional residue-producing chemical fumigants for controlling insect pests that attack stored grain, oilseeds, processed commodities, and packaged foods.
Hermetic storage of grain was practiced in ancient times in underground pits in the dry, subtropical regions of the Middle East and other dry regions of the world, such as Africa and India. Underground pits for grain storage were still used in Egypt in the 1940s, as described by Attia (1948). Very old but active hermetic storages were reported to be in operation in India (Girish, 1980) and in Yemen, Somalia, Sudan, and Egypt (Kamel, 1980). It has been suggested that, in Biblical times, Joseph employed hermetic storage for the preservation of the large grain reserves in Egypt during the seven years of plenty (Calderon, 1990).
The pioneers in the use of MAs in modern times considered the method to be an adaptation of the old principle of hermetic storage (Attia, 1948; Hyde and Daubney, 1960). One of the enthusiastic promoters of the hermetic-storage principle was the renowned French entomologist P. Vayssiere (1948). In his article in the first publication by the Food and Agriculture Organization of the United Nations on grain storage, he called hermetic storage “the process of the future for protection of foodstuffs.” The scientific and practical aspects of the MA method for food preservation were reviewed intensively in the 1950s by Oxley (1948), Bailey (1955), and Hyde et al (1973). Later, Sigaut (1980) stated that, in preindustrial times, hermetic storage was probably one of the means of keeping large quantities of grain free from insect attack for significant lengths of time in areas with mild winters. He also reported that the first large-scale tests were run in underground pits in Paris from 1819 to 1830. This principle was also used on a large scale in Argentina during and after World War II, when facilities were constructed and used for the underground hermetic storage of over 2.5 million tonnes of grain (Lopez, 1946; Anonymous, 1949). More-modern concrete hermetic-storage bins built primarily for famine protection have been constructed in Cyprus and Kenya for corn storage and are continuously in operation (De Lima, 1980).
Studies in the 1860s on modifying atmospheres by adding N2 or “burned air” to grain storages were also reported by Sigaut (1980). However, serious interest in using the technique in a practical, routine manner was not pursued until the 1950s and 1960s, probably due to the success of conventional fumigants and grain protectants in controlling stored-product pests. During this period, people began to realize that the chemicals, if used improperly, left objectionably residues, that they were hazardous to apply, and that there was a potential for the development of insect resistance to them. Research on the use of MAs was initiated during this time in Australia and in the United States and is ongoing in these and several other countries. This research has significantly restricted the use of chemicals in food. An important development stimulating further work on MA took place in the United States in 1980 and 1981. The Environmental Protection Agency approved an exemption from tolerance for CO2, N2, and products from an “inert” gas generator when used to control insects in raw (Federal Register, 1980) and processed (Federal Register, 1981) agricultural products.
MA and controlled atmosphere (CA) treatments for the disinfestation of dry stored products have received increasing scientific attention during the last 25 years. Although this method has become well established for control of storage pests, its commercial use is still limited to a few countries (Navarro et al, 1979; Shejbal, 1980b; Banks and Ripp, 1984; Jay and d’Orazio, 1984; Fleurat Lessard and Le Torc’h, 1987; Adler et al, 2000). Reviews on stored-product protection with MAs can be found in the publications of Bailey and Banks (1975, 1980); Jay (1980, 1984a,b), Banks (1981, 1983a,b), Annis (1987), Calderon and Barkai-Golan (1990), and Adler et al (2000).
The widespread scientific activities on this subject resulted in several international conferences, such as the International Conference on Controlled Atmospheres and Fumigation, which was held in 1980 in Rome, Italy (Shejbal, 1980a); in 1983 in Perth, Australia (Ripp et al, 1984); in 1989 in Singapore (Champ et al, 1990); in 1992 102 / Chapter 11 in Winnipeg, Canada (Navarro and Donahaye, 1993b); in 1996 in Nicosia, Cyprus (Donahaye et al, 1997); and in 2000 in the United States in Fresno, CA (Donahaye et al, 2001). New research findings on CAswere also reported at the International Working Conferences on Stored-Product Protection held in the United States in Savannah, GA, in 1974 (Anonymous, 1975); in Ibadan, Nigeria, in 1978 (Davis and Taylor, 1979); in Manhattan, KS, United States, in 1983 (Anonymous, 1984); in Tel Aviv, Israel, in 1986 (Donahaye and Navarro, 1987); in Bordeaux, France, in 1990 (Fleurat-Lessard and Ducom, 1991); in Canberra, Australia, in 1994 (Highley et al, 1994); in Beijing, China, in 1998 (Zuxun et al, 1999); and in York, United Kingdom, in 2002 (Credland et al, 2003). The annual research conferences on methyl bromide alternatives in the United States also provide a forum to enhance technology transfer (MBAO, 2003). These meetings served for the fruitful exchange of information among the participating scientists and the reciprocal insemination of new ideas for further research. The continuing interest in MAs led to the updating of this chapter, based on the text written by my friend, the late Ed Jay (Jay, 1984a). I wish to dedicate this chapter to his memory.
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