Division of Entomology, Indian Agricultural Research Institute, New Delhi-110 012 (India).
*A part of approved Ph.D. Thesis submitted by J.P. Singh to the Post-graduate School, Indian Agricultural Research Institute, New Delhi (India).
Field trials conducted in two crop seasons during 1990 and 1991 with upland cotton variety Pusa-31 to study the impact of insecticides on the intermittent population of jassid and whitefly during reproductive phase of the crop. Amongst the insecticides used in different spray schedules, cyhalothrin (50 g a.i./ha), monocrotophos (500 g a.i./ha) and endosulfan (750 g a.i./ha) were most effective in suppressing jassid population significantly up to 15 days and 10 days, respectively. The use of other insecticides, viz., fenvalerate (75 g a.i./ha), cypermethrin (60 g a.i./ha), alphamethrin (25 g a.i./ha), deltamethrin (12.5 g a.i./ha), triazophos (600 g a.i./ha) and deltaphos (250 g a.i./ha) failed to suppress jassid population 5 days after their application. Two neem products namely, margocide OK (80% EC @ 10 ml/I) and margocide CK (20% EC @ 5 ml/I) not only failed to combat the population of jassid and whitefly but rather revealed an increase in their population 2 days after application. Among all the treatments, triazophos showed promising results against whitefly. In general, population build-up in whitefly was more in those plots which received synthetic pyrethrdds as last spray, the maximum build-up was noted in fenvalerate-treated plots followed by deltamethrin, cypermethrin and cyhalothrin-treated plots.
