Storage of pigeonpea grain (Cajanus cajan (L.) Millsp.) in hermetic triple-layer bags prevents losses caused by Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Dry pigeonpea grain is susceptible to infestation from the cowpea bruchid during storage. This study investigated the potential of Purdue Improved Cowpea Storage (PICS™) and polypropylene (PP) bags for reducing insect infestation under ambient laboratory conditions for six months. Some of the bags were artificially infested with cowpea bruchid Callosobruchus maculatus (PICS1, PP1) while others were not (PICS0, PP0). In an additional trial, PP bags containing pigeonpeas were treated with Actellic Super^® dust before being artificially infested (PP1Ac). Moisture content, number of live C. maculatus adults, grain damage, and weight loss were determined at monthly intervals. Temperature and relative humidity (RH) in the PICS and PP bags were monitored continuously, while the oxygen and carbon dioxide concentrations in the PICS bags were measured at regular intervals. After six months moisture contents of pigeonpea grain stored in PP or PICS bags were not significantly different, and remained below 13%, the maximum required for safe storage of pigeonpeas. Adult C. maculatus populations increased rapidly in the PP bags, causing heavy seed damage. Percent damage after six months was 55, 96 and 76%, in PP0, PP1 and PP1Ac, corresponding to weight losses of 13.0, 26.2 and 13.5%, respectively. Actellic Super dust did not fully protect pigeonpeas against C. maculatus. By contrast, PICS bags halted multiplication of C. maculatus and subsequent seed damage and weight loss. PICS bags are an effective tool for preserving pigeonpeas against C. maculatus attack and their performance is superior to that of a single treatment with Actellic Super^® dust.