Presence and Effects of Chemical Toxin on Feeding of Cowpea Aphid, Aphis craccivora Koch (Homoptera: Aphididae) on Six Highly Resistant Varieties of Cowpea Vigna unguiculata (L) Walp, (Leguminosae)

Cowpea, Vigna unguiculata (L.) Walp is one of the most important grain legumes produced in Nigeria. It is mostly grown as a mixed crop with cereals in a traditional cereal/legume farming system. Cowpea aphid, Aphis craccivora Koch is the main aphid pest of cowpea. In view of the importance and serious damage caused by aphids, a total of 613 varieties of cowpeas were screened for resistance in International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. During the screening it was found that aphids died faster without reproducing and their longevity was very short on six varieties (Tvu 408 - P2, 801, 310, 266 - P1 2845 and 337-3F0 with high antibiotic properties. These varieties along with one susceptible variety (Tvu.76(Prima) were used for conducting two experiments together to find out the presence of a chemical and their role in aphid's feeding and survival. Comparative studies of the number of honey dew drops produced on varieties used in the experiment, and the reaction of the aphids in terms of probing time, longevity and number of nymphs produced on prima painted with the juice of the above mentioned highly resistant varieties, suggested that the resistance factor exists in the form of a toxin or a feeding deterrent. UNISWA Research Journal of Agriculture, Science and Technology Vol. 4 (1) 2000: pp 100-10