Synergistic effects of geographical strain, temperature and larval food on insecticide tolerance in Callosobruchus maculatus (F.)
This study investigated the multifactorial interaction of various environmental factors including geographical strain (Brazil, Cameroon and Yemen strains), temperature, dose and larval food (cowpea and mungbean) on the response of Callosobruchus maculatus adult to insecticide. All the main factors, their two-way interactions and the four-way interaction had significant effects on C. maculatus response to malathion (an organophosphate insecticide). However, the three-way interactions were not statistically significant (except strain × food × dose, P = 0.002). The Brazil strain was the most responsive to temperature irrespective of the larval food type. The impact of food type differs from one strain to the other; for instance, the food that imparts higher tolerance in a strain might reduce the tolerance in another. Likewise, the hierarchy of tolerance among the cowpea-reared strains (Brazil > Cameroon > Yemen) was totally different from that of the mungbean-reared strains (Cameroon > Yemen > Brazil). The reasons for these differences were discussed in the light of their impact on C. maculatus management. Both the management of C. maculatus and development of resistance could be complex; hence, the states of a variety of environmental factors need to be considered. This is necessary to maximize management success of this bruchid, especially in tropical/subtropical developing countries.