Effect of Insecticides on the Growth of Plant and Incidence of Bollworms in Cotton

Field studies were conducted during Kharif 1984 and 1985 at the Cotton Research Station, Sirsa (Haryana) to evaluate the effects of nine commonly used insecticides on phenology 01 tne new cotton variety ‘HSCP-1’, and to compare their bioefficacy and economics against the bollworms. Application of monocrotophos (450 and 300 g a.i./ha) ana enaosulfan (800 and 600 a.i./ha) led to more plant height (83.2 to 99.1 cm) and leaf surface area (LSA) (2261 to 3666 cm2) than the untreated control (70.2 cm plant height and 1818 cm2 LSA). Plots treated with these insecticides had lesser reduction in LSA (more retention of leaves) from maturity till last picking (70.3 to 81.3% reduction) in comparison to synthetic pyrethroids and control (84.9 to 90.7% reduction).

Fenvalerate and cypermethrin (@ 40 and 30 g a.i./ha) treated plots recorded lesser Fenvaleratelocule damage (<16%), fewer number of PBW (pink bollworm) diapausing larvae (<27 larvae/100 bolls) and higher seed cotton yield (32 q/ha). Amongst the conventional insecticides, fenitrothion and carbaryl (@1.0 and 0.8 kg a.i./ha) registered higner seed cotton yield (<25 q/ha), low bollworms incidence on locule basis (40%) and lesser number of diapausing PBW larvae (< 69 larvae/l Oa bolls) as compared with untreated control plots (17 q/ha yield, 69.4% incidence and 88.4 dia-pausing PBW withlarvae/10D bolls). Cost benefit ratios were 1:8.8, 1:13.6, 1:4.3, and 1:5.7 for fenvalerate, cypermethrin, fenitrothion and carbaryl, respectively.