Abstract

1Ndam, O.N.;Ogunwolu, E. O. and Manggoel, W

The effects of application of chlorpyrifos (50g a.i./ha), dimethoate (280g a.i./ha), cypermethrin (75g a.i./ha) and cypermethrin + dimethoate (37.5 + 140g a.i./ha) at mid – vegetative, 50% flowering and 50% podding on damage to and yield of soybean were assessed in 2000 and 2001 cropping seasons at the Teaching and Research Farm of the University of Agriculture, Makurdi. Experimental design was randomized complete block with each of five treatments (including unsprayed control) replicated four times. At the three growth stages of soybean, mean number of leaves plant-1 and percentage defoliation did not differed significantly. Mean number of leaves and defoliation ranged from 16-46 and 0.3-0.6, respectively. Similarly, treatment differences for soybean yield and yield parameters were not statistically significant (p >0.05), except for % malformed pods and %damaged seeds, with cypermethrin + dimethoate giving the lowest malformed pods (28.15%) and seed damage (10%). Our data showed very low level of defoliation (<1% on the average) due to insect pest feeding activities. However, seasonal variation in pest density and damage provided premise for reiterating rational basis for insecticide usage in soybean production in the study area.