Biology and life table parameters of Callosobruchus maculatus (F.) on Vigna unguiculata (L.) Walp. fertilized with some mineral- and bio-fertilizers

Abstract

Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae), a major pest of stored cowpea Vigna unguiculata (L.) Walp., causes critical losses by decreasing the grain weight, germination ability and nutritional quality. Improving host plant resistance by the application of appropriate fertilizers would be effective in reducing C. maculatus infestation. The effects of some mineral- (triple superphosphate (TSP) and urea) and bio-fertilizers (Bradyrhizobium japonicum, Pseudomonas putida, mycorrhizal fungi, and a mixture of them) were evaluated on the susceptibility of stored cowpea grains to C. maculatus. Cowpeas fertilized with examined fertilizers were cultivated at farm conditions. Then, the mature, dry grains were harvested and used to investigate the pest's life cycle and life table characteristics under 28 ± 1 °C, 65 ± 5% R.H., and total darkness. Developmental time of C. maculatus on TSP-treated grains was shorter than on control and P. putida treated ones. However, the lowest immature survival and fecundity (number of deposited eggs) was on TSP-fertilized grains. The intrinsic rate of increase (r) and net reproductive rate (R0) were the lowest on the grains treated with TSP. The highest tannins and starch content in the grains fertilized with TSP may be the critical reasons for their resistance to C. maculatus in storage. Application of TSP fertilizer can be recommended to increase cowpea resistance to this pest.