Synthetic pyrethroids and cotton bollworm control in Sri Lanka

Insecticidal control of cotton bollworms (Pectinophora gossyplella (Saund.), Heliothisarmigera (Hb.) and Farias vittella (F.)) was evaluated in the Southern Province of Sri Lanka for the period 1978–79. The standard schedule of 8–10 applications of 840 g a.i./ha monocrotophos was compared with monocrotophos (500 g a.i./ha); fenvalerate (100 and 200 g a.i./ha); permethrin (125 and 250 g a.i./ha); fenthion (1500 g a.i./ha); trichlorphon (900 g a.i./ha); methamidophos (840 g a.i./ha); profenofos (750ga.i./ha);profenofos + DDT(750ga.i./ha);and carbaryl (2240 g a.i./ha) in three trials with various schedules of application. Results were expressed as yield of seed cotton, percentage of damage to harvestable bolls and number of P. gossypiella larvae in opened bolls. Fenvalerate at the lower rate significantly reduced damage and larval infestation of bolls compared with the standard monocrotophos recommendation. It is suggested that fenvalerate or permethrin replace the monocrotophos recommendation since they are safer and give improved control.