Effects of nitrogen fertilization and some non-conventional insecticides on sap sucking pests and yield of transgenic Bt cotton in Sudan

Abstract

Integrated management of BT cotton pests was carried in field experiments during the seasons; 2016/2017 (Season I) and 2017/2018 (Season II) in the experimental research farm of Kassala University, Sudan. Four insecticides (imidacloprid, abamectin, profenofos and lufenuron) and three levels of soil applied nitrogen; 43.81 kgha−1, 87.62 kgha−1 and 131.43 kgha−1 were tested at recommended doses. Seven weekly counts of abundant pests (whitefly, jassid, aphid, and mealybug) were done starting 4 weeks before spraying. Post spray counts were done after 3, 10 and 17 days from spraying. Seed cotton yield of various treatments was recorded and economic analysis of the package was calculated. Results indicated that increasing the nitrogen dose result in significant increase in population of sap sucking pests during the pre-spray counts while insecticide treatments significantly reduced the infestation level in the post spray counts. Aphid was found in season I while mealybug was found in season II only in contrast to whitefly and jassid which were found in both seasons. Imidacloprid was the most effective insecticide causing reduction in the level of infestation by the various sap sucking pests in the range of 11.20% -71.66%, followed by lufenuron (with reduction in infestations level ranging between 8.12% to 69.11%) and profenofos (with infestation reduction ranging between 9.88% to 66.74%). On the other hand abamectin was the least effective treatment causing the least infestation reduction in the population of sap sucking pests (ranging between 8.38% to 66.45%). No significant interactions were found between nitrogen and insecticide treatments. Highest seed cotton yield and revenue was associated with imidacloprid combined with various nitrogen levels (causing 46%–63% increase), followed abamectin nitrogen treatments (7%–22%), profenofos and lufenuron nitrogen combinations. Generally, seed cotton yield increases by the increase of nitrogen dose, while the revenue (net benefit) depends on the price of the insecticide used.