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 ra w juices and chemical extracts of leaves of aphid-resistant (ICV-12) a nd aphid-susceptible (ICV-1) cultivars of cowpea [Vigna unguciculata L . (Walp.)], on the survival, growth, and reproduction of cowpea aphid Aphis craccivora Koch. Life table and demographic statistics of the co hort population and subsequent generations were estimated. Compared to ICV-I, the leaf juices and chemical extracts of ICV-12 exhibited sign ificant (P less than or equal to 0.05) adverse effects on aphid surviv al, growth, and reproduction. Raw leaf juice and ethyl acetate extract of ICV-12 in both water and sucrose significantly (P less than or equ al to 0.05) limited aphid performance. The adverse long-term effects w ere often more extreme than those resulting from a diet of distilled w ater alone. Methanol extract of ICV-12 showed an intermediate level of adverse effects on aphids, being generally less than that of ethyl ac etate but greater than that of hexane. Compared to the other ICV-12 ex tracts, the hexane extracts in water or sucrose media did not signific antly affect the aphid performance. Overall, it was determined that an tibiosis was a governing modality of aphid-resistance in ICV-12. Posti ngestive intoxication was caused by foliage components of seedling pla nts of that cultivar.