Efficacy of schedules of conventional insecticides and with synthetic pyrethroids against bollworm complex in cotton together with their persistence*

Field trials were conducted in two crop seasons during 1988 and 1989 with American cotton variety Pusa 31 and Egyptian cotton (19-8-4, a strain of intra barbadense cross) to study the efficacy of different schedules based on conventional insecticides and synthetic pyrethroids against bollworms. Different insecticides, viz., phorate granules (1 kg a.i./ha), dimethoate (0.04%), monocrotophos (500 g a.i./ha), endosulfan, phosalone and quinalphos (each 750 g a.i./ha), fenvalerate, cypermethrin and fenpropathrin (each 75 g a.i./ha), triazophos (600 g a.i./ha) and deltamethrin (12.5 g a.i./ha) were evaluated in a number of schedules. One spray of synthetic pyrethroid in a 4-spray schedule of dimethoate, monocrotophos, cypermethrin and endosulfan, and two sprays in 5-spray schedule of dimethoate, monocrotophos, cypermethrin, endosulfan and fenpropathrin alternated with conventional insecticides were most economical, safe and effective for the management of bollworm complex in American and barbadense cotton. The cost:benefit ratio on the basis of pooled data for two years was highest in such schedules, being 1:6.04 in American cotton and 1:4.37 in barbadense cotton. All the insecticides included in these schedules were well below their prescribed maximum residues limit. Insecticidal schedule of only conventional insecticides were ineffective against bollworms.