The effect of water stress on the development of cowpea aphid, Aphis craccivora Koch, on cowpea, Vigna unguiculata (L.) Walp

The study was conducted to see the effect of water stress on cowpea aphid,Aphis craccivora Koch on cowpea Vigna unguiculata (L.) Walp in International Institute of Tropical Agriculture IITA . For this study two weeks old cowpea seedlings were used. The seedlings were divided into three groups and the experiment was repeated three times. The experiment was initiated by releasing five fourth instar nymphs on each seedling,which were covered by cages.Once the introduced aphids had begun reproducing,one newly born aphid was retained in each cage and the remaining aphids including the adults were removed. The three groups were treated daily with 200ml, 100ml and 10ml of water respectively. There were fifteen replications of each treatment and the experiment was repeated twice. Developmental studies were conducted on individual aphids daily, until they died. The results showed that the water stress imposed by using 10 ml of water regime increased the duration of all the developmental stages but decreased the rate of reproduction of aphids thus lowering the fecundity significantly.