The Effect of Lentil-Tef Mixture on Occurrence of Adzuki Bean Beetle (Callosobruchus chinensis) and its Natural Enemy in Stored Lentil

Laboratory experiment was conducted to determine the effect of mixing lentil grain with tef grain on the occurrence of Adzuki bean beetle (ABB), Callosobruchus chinensis and its natural enemy in stored lentil. Brown-seed tef grain was mixed with lentil (cu. Derso) grain on replacement basis at the rate of 0% (full lentil), 5%, 10%, 15%, 20%, 25%, and 30% of the full lentil grain. The full lentil treatment was10 kg per bag (polypropylene bags (40 cm x 70 cm)), while for the remaining treatments the required amount of lentil grain was removed and replaced by equal amount of tef grain. Each treatment was replicated three times and was arranged in randomized complete block design. From each bag 25 lentil grain samples were randomly selected approximately at monthly intervals and examined for the presence or absence of ABB eggs, ABB emergence holes and its natural enemy emergence holes. Tef grain mixed (up to 30%) with lentil grain had no influence on the percentage of grains with ABB eggs (%); ABB eggs per grain; grains with emergence hole (%); ABB emergence hole per grain; and natural enemy emergence hole per grain. Dinarmus basalis, which is a new record to Ethiopia, and Anisopteromalus calandrae were the ectoparasitoids that attacked ABB larvae in stored lentil. The proportion of ABB larvae parasitized by the two natural enemies together ranged from 18% to 66%. Since ABB was able to infest, reproduce, and complete multiple generations on lentil irrespective of the amount of tef mixed farmer should be informed about the ineffectiveness of the traditional method they apply to control Adzuki bean beetle in stored lentil.