Resistance to the cowpea weevil (Callosobruchus maculatus) larva in pods of cowpea (Vigna unguiculata)

Thirty cowpea, Vigna unguiculata (L.) Walpers, cultivars were evaluated as intact pods to determine if any possessed resistance to the cowpea weevil, Callosobruchus maculatus (Fabr.). Pod resistance was measured as pre‐establishment larval mortality (PreM); those larvae dying after egg hatch but before penetrating into the seeds, and as post‐establishment within‐seed mortality (PostM); those larvae dying after penetrating into the seeds. Among the 30 varieties examined, PreM ranged from 57.9% to 99.4% and PostM ranged from 6.7%, to 82.6%. Ten varieties exhibited total intact pod mortality (mortality from egg hatch to adult emergence from the seed) greater than 95%. Physical measurements were made of several pod and seed characteristics to ascertain whether the observed pod resistance was due to seed factors, pod‐wall factors, or to interactions between the pod and seeds. Although resistance to breakage (from handling plus pod dehiscence) is a necessary characteristic for overall pod protection against C. maculatus; other factors are also important. Among the other pod and seed characteristics measured to identify major resistance factors, seed coat thickness was the one most highly correlated with pod resistance. Our results suggest that interactions between pod‐wall and seed coat characteristics play a large role in pod resistance of cowpeas to C. maculatus .