Environmental complexity on insecticide tolerance in Callosobruchus maculatus F. (Coleoptera: Bruchidae)

Our earlier study revealed significant environmental impact on insecticide tolerance in cowpea bruchid, Callosobruchus maculatus. Environmental factors such as geographical origin of strains, exposure temperature, rearing food type and quantity of toxicant were studied. Further study replaced the food type by varieties of its most common host i.e. cowpea, Vigna unguiculata (L.) Walp. There were similarities and differences in the response of the two geographical strains, Brazil and Cameroon. The varietal study revealed that tolerance of the Brazilian strain was consistently higher than that of Cameroon. Although this was not always significant, it was in contrast to what was obtained in the food type study. The effect of the interactions of different environmental factors on C. maculatus is quite complex. There is need for a critical approach to its control in the field or store.