Resistance of wild herbaceous legume to the cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae)
The aphid was reared on three wild herbaceous legumes species namely Crotalaria sphaerocarpa DC, Indigofera charlieriana Schinz, wild cowpea Vigna unguiculata subsp. Spontanea Harms) and cowpea variety "Inia" as a check. Life table parameters were used to assess resistance of the wild legumes against the cowpea aphid. The study showed that population growth and life table parameters differed significantly among legume species indicating variation in the level of cowpea aphid response to different species. Significantly longer pre productive period, reduction in fecundity and survival of the cowpea aphid were observed on I. charlieriana and C. sphaerocarpa indicating levels of resistance. A significant reduction in intrinsic rate of natural increase, net reproductive rate, as well as finite rate of increase occurred between varieties. Generation time and doubling time were also significantly higher on aphids feeding on I. charlieriana and C. sphaerocarpa compared to "Inia" and wild cowpea. The negative effects of I. charlieriana and C. sphaerocarpa on life table parameters of A. craccivora indicate degree of resistance of these species against the aphid opening new line of research.