Invasive Species Compendium

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Abstract

Use of biogenerated atmospheres of stored commodities for quality preservation and insect control, with particular reference to cocoa beans.

Abstract

Preliminary data for insect control and for quality preservation of stored cocoa beans is presented, as a methyl bromide alternative, by employing a novel approach through the use of biogenerated modified atmospheres. The respiration rates of fermented cocoa beans from Makassar, Sulawesi, Indonesia, were determined under laboratory conditions. Initial insect populations found in these cocoa beans samples consisted of Carpophilus spp., Ahasverus advena, Cryptolestes spp., and Psocids. Respiration rates of cocoa beans at equilibrium relative humidities (r.h.) of 59, 68, and 73% were determined at 26°C in hermetically sealed 1 L capacity jars containing 500 g commodity. At the equilibrium r.h. of 73%, the respiration of the cocoa beans depleted the oxygen concentration to <1% and increased the carbon dioxide concentration to 23% within six days. To obtain a similar oxygen depletion for cocoa beans at 68% equilibrium r.h, a duration of 23 days was required, while for the sealed cocoa beans in equilibrium with 59% r.h. the oxygen concentration after 23 days had only decreased to 10.8%. Under field conditions in a cocoa bean storage facility in Makassar, Indonesia, a hermetically sealed flexible structure containing 6.7 tonnes of cocoa beans at an initial moisture content of 7.3% (70% equilibrium r.h.) was monitored for oxygen concentration and quality parameters of the beans. The measurements showed a decrease in oxygen concentration to 0.3% after 5.5 days. No insects survived the oxygen depleted biogenerated atmosphere. These encouraging results reveal the possibility of utilizing biogenerated atmospheres in integrated pest management (OPM) for the quality preservation (by preventing the development of FFA, moulds, and mycotoxins), and insect control of cocoa pests.