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The effect of eight deltamethrin spray schedules on cowpea seed yields and the percentage loss in potential seed yield due to damage by seed insect pests, was evaluated on five cowpea (Vigna unguiculata (L) Walp) cultivars, in Foumbot, Cameroon, in 1988Cameroon, in , 1989Cameroon, in and 1990 In each year, sprayed plants outyielded the unsprayed plants and the overall percentage loss in potential seed yield was significantly (P > 0.05) higher in unsprayed than sprayed plants. The spray schedules of one deltamethrin spray at either 75-100% flowerbud and one at 75-100% podding stage or one spray at 75-100% flowering stage, and one at 75-100% podding stage, increased seed yield and low percentage loss in potential seed yield as much as was obtained by spraying plants fortnightly with deltamethrin at the preflowering and reproductive phases of growth.

The effects of feeding by groups of 0, 15, 30, 45, 60, 75 or 90 adults of Empoasca dolichi Paoli per plant on the growth and yield of caged Prima and Ife Brown cowpea plants infested 14, 21 or 28 days after planting were studied in Ibadan, Nigeria. Caging had no significant adverse effects on yield. E. dolichi caused severe hopper-burn in plants infested 14 days after planting. The mean pre-flower-opening stage lasted 42-1, 38-0 and 39-0 days in Prima and 446, 407 and 423 days in Ife Brown plants infested 14, 21 and 28 days after planting, respectively, the first figure for each cultivar being significantly different from the other two. The mean yields were 23 3, 28 5 and 298 pods per plant for Prima, and 350, 48-1 and 437 for Ife Brown, respectively, the first figure for each cultivar being significantly lower than the other two. The reduction in seed yield in damaged plants infested 14 days after planting ranged from 287 to 413% for Prima and 272 to 56-9% for Ife Brown, the reductions being significantly correlated with scores for feeding damage by E. dolichi.