Management of Insect Pests using Chlorpyrifos Applications at Different Growth Stages of Tomato, Solanum lycopersicum L.

Field studies were conducted in Kumasi, Ghana in the major and minor planting seasons of 2013 to evaluate the effect of chlorpyrifos applications at different growth stages of tomato (Solanum lycopersicum L) for the management of insect pests. The treatments were: Chlorpyrifos at 1.5 ml / 0.5 litre of water applied (i) at the vegetative growth stage only (sprayed vegetative), (ii) at the reproductive growth stage only (starting at 50 % flowering (sprayed reproductive) and (iii) throughout the crop’s growth period (sprayed throughout). A control plot that received only water was also maintained. In both seasons, significantly (P < 0.05) less number of Bemisia tabaci Gennadius and Thrips tabaci Linderman were collected from the insecticide-treated tomato plots than the untreated, control plots, but no significant differences were observed among the treatments in the aggregations of Aphis gossypii Glover and Helicoverpa armigera (Hubner). Chlorpyrifos application in the sprayed throughout plots significantly (P < 0.05) reduced damage to tomato fruits in the major season but not in the minor season. Tomato fruits from the sprayed vegetative and sprayed reproductive plots had comparable damage as the fruits from untreated control plots. Chlorpyrifos application also significantly (P < 0.05) increased yield of tomato from the sprayed throughout plots in both seasons. The best protection to the crop against the insect pests was obtained from weekly applications of chlorpyrifos throughout the growth period of the crop (sprayed throughout plots). Key words: Tomato, Chlorpyrifos, insect pests, management, population dynamic