Natural occurrence of ectoparasitoids of Adzuki bean beetle (Callosobruchus chinensis L.) in stored chickpea (Cicer arietinum L.)

In Ethiopia the Adzuki bean beetle, Callosobruchus chinensis causes 8% weight losses in chickpea stored for six to eight months. But biological control agents associated with stored chickpea are not known. In this study, the identity of ectoparasitoid species that parasitize C. chinensis and the effect of cultivars on the extent of C. chinensis parasitism by ectoparasitoids in stored chickpea are reported for the first time in Ethiopia. There were 21 grain-filled bags for each cultivar Arerti and Natoli. From each bag, 25 to 30 seeds were taken at random from the top surface. Then each grain was examined and categorized in to four classes as sound grain, with Adzuki bean beetle exit hole, natural enemy exit hole, and both Adzuki bean beetle and natural enemy exit holes. From these data percent damaged grains and percent parasitized Adzuki bean beetle larvae were estimated. Natural enemies were collected using aspirator for identification. Dinarmus basalis (Rondani) and Anisopteromalus calandrae (Howard) were the ectoparasitoids that attack Adzuki bean beetle larvae in stored chickpea. In all sampling dates, chickpea cultivar significantly affected both the proportion of grains infested by Adzuki bean beetle and the degree of parasitism of Adzuki bean larvae by the ectoparasitoids. On Arerti and Natoli, 5 to 15% and 17 to 55% of the grains, respectively, were infested. The proportion of Adzuki bean beetle larvae parasitized by the two ectoparasitoids on cultivar Arerti ranged from 66 to 98%; while on Natoli only 17 to 47% of the larvae were parasitized.