Wheat stored in triple layer plastic bags: Protection against the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae) and the effect of air leaks on hermetic storage

Martin, Daniel Thomas M.S., Purdue University, May 2014. Wheat Stored in Triple Layer Plastic Bags: Protection Against the Rice Weevil, Sitophilus oryzae L. (Coleoptera: Curcilionidae) and the Effect of Air Leaks on Hermetic Storage. Major Professor: Dr. Larry L. Murdock. The Purdue Improved Crop Storage system is a triple layer high-density polyethylene storage technology that has proven to be an effective means of protecting cowpea [Vigna unguiculata subsp. unguiculata (L.) (Walp)] from damage caused by the cowpea bruchid [Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae)] during storage. PICS bags work due to the exclusion of oxygen, which deprives insects of metabolic energy and of their water supply. The effectiveness of this hermetic storage technology has led to widespread adoption across West Africa. Its popularity has led lowincome farmers in the Sub-Saharan zone to ask if the bags can be used to store other commodities in addition to cowpea. In the first chapter, I present results from trials testing the extent to which PICS technology is effective for protecting stored wheat from rice weevil [Sitophilus oryzae (L.) (Coleoptera: Curcilionidae)]. Farmers who used PICS bags for cowpea observed that repeated use and insect damage can lead to tiny holes in the walls of PICS bags. Slightly damaged bags may still protect stores of grain, but may be less effective in excluding oxygen. The volume of grain stored may also affect the rate of oxygen leakage into the grain. In the second chapter, I describe: (1) the effect of small,