Abstract
Three early pigeon pea [Cajanus cajan (L.) Millsp.) genotypes were sown at four different dates, beginning with the early rains in 1992 and 1993. The trials were carried out in the northern Guinea savanna ecology of Ghana. One trial, serving as a check, was protected from insects with three sprays of KarateR insecticide at 12 g active ingredient ha-1, whilst the other was not. Pod yield and its components including reproductive duration (RD), crop growth rate (CGR), partition coefficient (p), and harvest index (HI) were determined. The aim was to use these physiological knowledge on the crop in addition to manipulation of the sowing dates to determine an appropriate insect control strategy. The results indicated that early planting did not have any effect on insect damage. In 1992, most yield and yield components were adversely affected by the damage caused by Mylabris pustulata Thunb. and Helicoverpa armigera Hub., in addition to drought. Although Maruca testulalis Geyr. was also observed on the crop, it did not appear to have caused any serious damage. None of the insects had effect on CGR but adversely affected p and HI, indicating effective insect control should start at floral bud initiation stage.
