Studies on the legume pod-borer, Maruca testulalis (Geyer)—VIII. Cowpea phenology and yield loss assessment: effect of loss of leaves, shoots, flowers and pods on cowpea yield in Western Kenya

Abstract

Preliminary studies were conducted using four varieties of potted cowpea (Ex-Luanda, Katuli 107. Vita 1, TVx66-2H) to determine plant response to injury to foliar and reproductive structures. Several levels of leaf loss were simulated at two plant growth stages; flowers were excised manually for 10. 15 and 20 consecutive days post-flowering; and pods were removed at several levels, 7–10 days after flowering. Similar tests were carried out during the short rains of Mbita Point Field Station (MPFS) and on a farmer’s field at Kodiera, near Homa Bay, using two varieties—a local indeterminate dual purpose type (Ex-Luanda) and a determinate grain cultivar (TVu 1509). Defoliation significantly decreased plant weight and pod and grain production, but not branching and pod dimensions of potted plants. Flower and pod loss did not markedly lower plant weight, pod and seed production, and the effect on branching was negligible. The response of field plants was strongly influenced by crop variety and environment, notably agronomic practices and location. These results have implications for integrated pest management (IPM) which are explored in the context of increased grain legume production.