Effect of chlorpyrifos application at different growth stages on Insect Pests’ incidence, Damage and yield of tomato (Solanum Lycopersicum L) and Okra (Abelmoschus Esculentus L)

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Field studies were conducted at the Plantation Crops Section of the Department of Crop and Soil Sciences (KNUST), Kumasi in the major and minor planting seasons of 2013 to evaluate the effect ofChlorpyrifos applications at different growth stages of okra (Abelmoschus esculentus L) and tomato (Solanumlycopersicum L) for the management of insect pests of the two crops. The treatments were: Chlorpyrifos at 1.5 ml / 0.5 l of water applied (i) at the vegetative stage of the crops (sprayed vegetative), (ii) at the reproductive growth stage of the crops (starting at 50 % flowering of the crops – sprayed reproductive) and (iii) throughout the crops’ 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 difference was observed among the treatments in the aggregations of Aphis gossypii(Glover) and Helicoverpa armigera (Hubner).With respect to okra, significantly (P < 0.05) fewerT. tabaci, B. tabaci, A. gossypii and Podagrica spp. were collected from the sprayed throughout plots than the other treatment plots, in the major season. Similar results were obtained in the minor season. Over 99 % of the Podagrica species collected on okra were P. uniformis(Jacoby). 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. Significantly (P < 0.05) less percent defoliation was recorded on the insecticide-treated plots than the untreated control plots in both seasons. However, significant increase in yield of okra was obtained from only the sprayed throughout plots, but no significant differences were obtained in the number of damaged okra fruits. The best protection to the crops against the insect pests was obtained from weekly applications of chlorpyrifos throughout the entire growth period of the crops(sprayed throughout plots).
Thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture KNUST, Kumasi in partial fulfilment of the requirement for the award of MSc. Crop Protection (Entomology)