The present study allowed evaluating the efficacy of five plant water extracts on aphids and the yield of six cowpea’s cultivars in three villages of the northwest region of Benin. The five aqueous extracts made with Hyptis suaveolens, Azadirachta indica, Manihot esculenta, Thevetia neriifolia and Cymbopogon nardus have been compared to the control treatment without product with six producers in a scattered experimental randomized blocks. The number of aphids present on the cowpea plants at 27, 34, 41, 48, 55 and 62 days after sowing, and the cowpea seeds yield was estimated. Results indicated that aqueous extracts of Thevetia neriifolia, Azadirachta indica, Hyptis suaveolens and of cassava have very significantly (p < 0.001) reduced the populations of aphids. Katché péha, Kpodjiguèguè, Katché sôwôho and Toura pera are been the least attacked by pests. Aqueous extracts of Thevetia neriifolia, Hyptis suaveolens, Azadirachta indica, cassava, Cymbopogon nardus and the control led in this order, decreasing seeds yields from 886 kg/ha to 387 kg/ha. Seeds yields of cultivars Katché péha, Kpodjiguèguè, Katché sôwôho, Toura pera, Katché péha nan soorii and Katché Sénégal were very significantly (p < 0,001) variable in this order, from 747.50 kg/ha to 519 kg/ha. These aqueous extracts should be tested on thrips and on the bugs as well as for the future of the seeds in stock for a good protection of cowpea.
