FIELD INFESTATION AND DAMAGE TO SOYBEAN AND COWPEA BY POD-SUCKING BUGS IN BENUE STATE, NIGERIA

Soybean, Glycine max (L.) Merril, and cowpea, Vigna unguiculata (L.) Walp., were grown in field plots in 1988 and 1989 to compare infestation and damage by pod-sucking bugs (PSBs). Population of PSB was monitored by counting adults and nymphs on rows two and six of each plot from 5 to 14 weeks after planting. Cowpea was infested mainly by Clavigralla tomentosicollis (Stal.), C. shadabi (Germ.), Mirperus jaculus (Thnb.) and Aspavia armigera F., while soybean was infested by M.jaculus, Anoplocnemis curvipes (F.) and Riptortus dentipes F. Soybean had exceedingly low PSB density, < 1 bug/2 m-row, in 1988 and 1989. Four sprays of 400 g a.i./ha. dimethoate had no significant effect on pod and seed damage, yield and germination, compared to the unsprayed control. In contrast, cowpea attracted high populations of PSBs, 30 and 1 bug/2 m-row, in 1988 and 1989, respectively. Dimethoate sprayed against PSBs on cowpea resulted in two- to four-fold reductions (P < 0.05) in pod and seed damage and yield increases of 1500 kg/ha. (P < 0.05) in 1988 and 300 kg/ha. (P < 0.05) in 1989.