Reproductive performance and population dynamics of cowpea aphid (Homoptera: Aphididae) on leaf extracts of resistant and susceptible cowpeas.

Membrane feeding studies were conducted to determine the effects of raw juices and chemical extracts of leaves of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpea [Vigna unguiculata L. (Walp.)], on the survival, growth, and reproduction of cowpea aphidAphis craccivora Koch. Life table and demographic statistics of the cohort population and subsequent generations were estimated. Compared to ICV-1, the leaf juices and chemical extracts of ICV-12 exhibited significant (P<-0.05) adveres effects on aphid survival, growth, and reproduction. Raw leaf juice and ethyl acetate extract of ICV-12 in both water and sucrose significantly (P<-0.05) limited aphid performance. The adverse long-term effects were often more extreme than those resulting from a diet of distilled water alone. Methanol extract of ICV-12 showed an intermediate level of adverse effects on aphids, being generally less than that of ethyl acetate but greater than that of hexane. Compared to the other ICV-12 extracts, the hexane extracts in water or sucrose media did not significantly affect the aphid performance. Overall, it was determined that antibiosis was a governing modality of aphid-resistance in ICV-12. Postingestive intoxication was caused by foliage components of seedling plants of that cultivar.