Effect of Water and Pests Stresses on Cowpea Yield

In order to investigate the effect of pest and water stresses on different growing stages of cowpea (Vigna sinensis) and pest occurrence، an experiment was conducted in Khazaneh Research station of Isfahan University of Technology. The experiment was carried out in a factorial complete randomized block design، in two different farms، with and without insecticide application. The treatments included severe water stress (50% water requirement)، moderate water stress (75% water requirement) in four stages of cowpea growth، the first stage (from seed germination until flower in، second stage (from flowering until pod-filling)، third stage (from pod-filling until harvesting) and the whole period of cowpea growth، in three replications. There was a control treatment in each farm with no stress in the whole period of cowpea growth، in three replications. The results showed that water stress had no significant effect on percentage of protein and mineral material. Result also showed that water stress had a significant effect (P≤ 0. 01) on population of insects. Water stress significantly (P≤ 0. 01) reduced the population of nymphs and adults of Empoasca decipiens Paoli and leaf minor damages، but water stress increased population of Thrips tabaci Lind. Considering the duration of first stage of growth (63 days)، it is concluded that this stage had less sensitivity to water stress than the other stages. In regions، where farmers encounter water shortage for cowpea planting، the best performance can be obtained when moderate water stress (75% water requirement) is applied at the first stage of growth.