Age-dependent changes in feeding preference and effects of commercial semi-synthetic diets on development of the legume pod borer,Maruca vitrata (Lepidoptera: Crambidae)

Mass rearing of the legume podborer Maruca vitrata (Fablicius) can be a very labor-intensive process. To improve the labor-saving method for larval raising, rearing experiments were conducted using 14 diet regimens, with and without diet-switching between the earlier and latter larval stages. Six different semi-synthetic diets were used, including four crude commercial diets. Larvae showed the highest performance in survival rate, developmental duration and pupal weight when reared on the following diet regimen: (1) 1st to 2nd instars—Insecta F-II (a commercial semi-synthetic diet for herbivorous insects, containing no mulberry leaf powder) mixed with 50 % azuki bean powder; (2) 3rd to 5th instars—switch to a crude commercial diet, either Insecta LFS (a semi-synthetic diet for herbivorous insects, containing mulberry leaf powder) or Insecta F-II mixed with 10 % azuki bean powder. In the feeding experiments, larvae in the earlier stages tended to prefer diets containing azuki bean or mulberry leaf powder, whereas larvae in the latter stages were non-selective in their feeding preference. The exception was Insecta F-II mixed with 50 % azuki bean powder, for which the larvae showed a significantly high preference between 24 and 96 h following release.