Miss. Nitta Anusha
Background: The spotted pod borer Maruca vitrata Fabricius (Lepidoptera: Crambidae) is a serious pantropical pest of legume crops. A suitable semisynthetic diet is desirable for producing uniform insects for commercial purposes or research.
Results: To mass rear M. vitrata under laboratory conditions, a study was carried out and aimed to develop a blackgram- based semisynthetic diet (D-B). Comparison of several biological, reproductive and digestive parameters for three successive generations of M. vitrata reared on four different semisynthetic diets, viz., D-J, D-JR, D-NEW, black gram- based semisynthetic diet (D-BAS) and black gram natural diet, was successfully attempted. Larvae fed a blackgram-based semisynthetic diet (D-BAS) recorded the shortest developmental time (29.37 days) and the highest food consumption (64.21 mg) and fecal production (20.83 mg), resulting in the maximum larval and pupal weights (48.46 and 47.11 mg, respectively). The insects fed the D-NEW and blackleg natural diets recorded the longest developmental period (32.90 and 34.48 days) with minimum larval weights (44.03 and 48.64 mg) and pupal weights (40.39 and 49.43 mg), respectively. The highest percent pupation (82.53), adult emergence (78.22), larval (6.50) and pupal growth index (12.86) were recorded for larvae fed a blackgram-based semisynthetic diet (D-BAS). The highest sex ratio (1.81) and fecundity (43.94 eggs) were recorded on the blackgram semisynthetic diet (D-BAS). The highest relative consumption rate (0.23 gg-1day-1), relative growth rate (0.084 gg-1day1), relative metabolic rate (0.073 gg-1day-1), approximate digestibility (67.49%) and metabolic costs (46.51%) and lowest efficiency of conversion of ingested food (36.09%) and efficiency of conversion of digested food (53.49%) were recorded for the blacklegy semisynthetic diet (D-BAS).
Conclusions: A black gram-based semisynthetic diet was found to be superior, exhibiting a high rate of egg production, growth, survival and reproduction compared to other diets, but was not significantly better than the natural diet with black gram flowers. The blackgram-based semisynthetic diet was suitable for the continuous rearing of M. vitrata to produce uniformly sized insects of predictable performance without a loss of vigor or a decline in reproductive potential. A blackgram-based semisynthetic diet can be used as an efficient alternative to a natural diet for rearing in laboratory conditions.