Department of Crop Protection, University of Maidguri, P.M.B 1069, Maiduguri, Borno State, Nigeria; College of Agriculture, P.M.B. 1427, Maiduguri, Borno State, Nigeria
Sharah, H.A., Department of Crop Protection, University of Maidguri, P.M.B 1069, Maiduguri, Borno State, Nigeria; Ali, E.A., College of Agriculture, P.M.B. 1427, Maiduguri, Borno State, Nigeria
Field experiment was carried in Maiduguri during two cropping seasons to assess crop - pest cycle in relation to pest control using insecticides in cowpea [(Vigna unguiculata L. (Walp)]. The factional experiment considered two types of insecticides (Decis: deltamethrin and Nogos: dichlorvos) and nine (9) spraying regimes. The four stages in the phenology (pre-flowering (vegetative), flowering, podding & maturation) were monitored closely until harvest. Flower and pod drops were significantly different between control and treated plots and the cost: benefit ratios also followed similar trends. Pest species were more abundant at the pre-flowering and maturation in all the treatments, whether chemically treated or not. A total of 14,400 insect species were counted from the 50 observations in the two seasons and grouped into six orders, listed in order of abundance. Thysanoptera topped the list and diptera was the least in abundance. Insect populations were higher in the untreated (control) plots than in all the two-sprayed fields with 18.3% and 10.3% more between the un-sprayed (control; T0) and the complete controlled (T8) for Decis and Nogos treated plots, respectively. A significant interaction existed between insecticides types and spray regimes as there was low insect number per plant in Decis-treated plots than in Nogos treated plots. Flower and flower drops, pods and pods drops and cost: benefit ratios were significantly different with spaying regimes irrespective of the chemicals. Decis treated fields had better protection from Nogos treated fields.