IMPACT OF CHLORPYRIFOS APPLIED AT DIFFERENT GROWTH STAGES ON INSECT PESTS OF OKRA (Abelmoschus esculentus 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 okra (Abelmoschus esculentus L.) for the management of insect pests of the crop. The treatments were: Chlorpyrifos at 1.5 ml/0.5 litre water applied (i) At only the vegetative growth stage of the crop (sprayed vegetative), (ii) At only the reproductive growth stage of the crop (starting at 50% flowering of the crop – sprayed reproductive) and (iii) Throughout the crop’s growth period (sprayed throughout). A control plot that received only water was also maintained. Two species of Podagrica - P. uniformis Jacoby and P. sjostedti Jacoby - were collected but over 99% of them were the former. In the major season, significantly fewer Bemisia tabaci Gennadius and Podagrica spp. were collected from the sprayed throughout plots than the other treatment plots whilst significantly fewer Thrips tabaci Gennadius were collected from the insecticide-treated than the control plots. In the minor season, significantly more Podagrica spp. were collected from the sprayed throughout plots than the other treatment plots whilst significantly more B, tabaci aggregated on the leaves of the plants of the sprayed throughout and sprayed reproductive plots than the control plots. Significantly lesser percent defoliation was recorded on the insecticide-treated plots than the control plots in the major season but the results were mixed in the minor season. Even though significant increase in yield of okra was obtained from only the sprayed reproductive plots, no significant differences were obtained in the number of damaged okra fruits.