STATUS OF INSECTICIDE RESISTANCE IN THE COTTON BOLLWORM, HELICOVERPA ARMIGERA (HUBNER)
2007, 8 (2) p. 171-182
The status of insecticide resistance in some fi eld populations of Helicoverpa armigera (Hubner) from the main cotton growing regions of central and south India was determined during the cropping seasons of 2001-2005. Seven insecticides viz. endosulfan, methomyl, monocrotophos, quinalphos, chlorpyriphos, fenvalerate and cypermethrin were tested against second-, third- and fi fth-instar Helicoverpa armigera larvae. Dose-mortality regressions, LD50s and their fi ducial limits were computed by probit analysis. Resistance factors (RF) were estimated at the LD50 level as RF=LD50 fi eld strain/LD50 susceptible strain. The Helicoverpa armigera (Hubner) exhibited widespread resistance (RF=48-919) to cypermethrin. Insecticide resistance to chlorpyriphos was low to moderate in the majority of the strains tested. A substantial inter-strain variation in insecticide resistance was evident.