Insect pest incidence on cowpea in the cameroonian southwest forest and western derived savanna zones, their contribution to yield loss in Foumbot and their control

摘要

In 1986 and 1987, insect pests sampled on cowpea in the Cameroonian Southwest forest and Western derived savanna ecological 1 zones included Maruca vitrata, Leguminivora (Cydia) ptychora, Helicoverpa (Heliothis) armigera, Melanagromyza vignalis, Apion disjunctum, Aphis craccivora, heteropteran bugs and bruchids. Under eight different deltamethrin spray schedules evaluated for their control at Foumbot, western derived savanna ecozone, the yield loss they caused ranged from 123.60 kg/ha in plants sprayed twice at the reproductive stage to 362.51 kg/ha in unsprayed plants in 1988; 21.86 kg/ha in plants sprayed thrice at the reproductive stage to 90. 73 kg/ha in unsprayed plants in 1989 and 91.72 kg/ha in plants sprayed 5 to 6 times at fortnightly intervals, to 184.08 kg/ha in unsprayed plants in 1990. The percentage loss due to Maruca vitrata, Melanagromyza vignalis and heteropteran bugs was high in sprayed and unsprayed plots. In 1989 and 1990, seed yields were significantly increased by spraying deltamethrin either forthnightly, or once at 75-100% flowerbuds and once at 75-100% podding, or once at 75-100% flowering and once at 75-100% podding.