Survival and development of Campoletis chlorideae on various insect and crop hosts: implications for Bt-transgenic crops

The parasitic wasp, Campoletis chlorideae is an important larval parasitoid of Helicoverpa armigera a serious pest of cotton, grain legumes and cereals. Large-scale deployment of Bt-transgenic crops with resistance to H. armigera may have potential consequences for the development and survival of C. chlorideae. Therefore, we studied the tritrophic interactions of C. chlorideae involving eight insect host species and six host crops under laboratory conditions. The recovery of H. armigera larvae following release was greater on pigeonpea and chickpea when compared with cotton, groundnut and pearl millet. The parasitism by C. chlorideae females was least with reduction in cocoon formation and adult emergence on H. armigera larvae released on chickpea. Host insects also had significant effect on the development and survival of C. chlorideae. The larval period of C. chlorideae was prolonged by 2-3 days on Spodoptera exigua, Mythimna separata and Achaea janata when compared with H. armigera, Helicoverpa assulta and Spodoptera litura. Maximum cocoon formation and adult emergence were recorded on H. armigera (82.4% and 70.5%, respectively) than on other insect hosts. These studies have important implications on development and survival of C. chlorideae on alternate insect hosts on non-transgenic crop plants, when there is paucity of H. armigera larvae on transgenic crops expressing Bt-toxins

Micronutrient needs of tropical food crops

The trace element requirements of tropical crops are reviewed with special reference to their role, the differences between crop species, the differences between cultivars, paths of trace element uptake, effects of climate, the importance of crop management and yield levels