New artificial diet for continuous rearing of the bean pod borer, Maruca vitrata

The bean pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), is a serious pantropical pest of grain legumes. A suitable artificial diet is desirable for producing uniform insects for commercial purposes or research. Three previously described artificial diets, 1 newly-developed artificial diet, and cowpea (Vigna unguiculata (L.) Walp. (Fabales: Fabaceae)), the natural hostplant of M. vitrata, were used for rearing M. vitrata, and the life parameters were examined. The results indicated that insects completed a full life cycle only when the larvae were fed cowpea or the diet reported by Onyango and Ochieng'-Odero ( 1993 ), called the "D-OO diet." However, the rearing efficiency (i.e., larval and pupal survival, longevity of adults, and fecundity) on the D-OO diet was inferior to the rearing efficiency on cowpea. Subsequently, a new artificial diet was formulated based on soybean powder, Glycine max (L.) Merr. (Fabales: Fabaceae), and wheat germ, Triticum aestivum L. (Poales: Poaceae). The egg production, egg hatching, larval developmental duration, and pupal survival of the M. vitrata reared on the new artificial diet were found to be significantly improved relative to the D-OO diet, but were not significantly better than on the host-plant cowpea. The optimum rearing density was 15-25 larvae per box. There were no significant changes in reproductive potential after 8 successive generations of rearing on the new diet. These results indicated that the newly developed diet could serve as a viable alternative to cowpea plant for continuous rearing of M. vitrata.