Carbamate and organophosphate resistance in cotton pests in India, 1995 to1999

Monitoring for organophosphate and carbamate resistance was carried out on five major insect pests of cotton collected from 22 cotton-growing district s across India. Resistance was monitored in Helicoverpa armigera (Hubner) a nd Pectinophora gossypiella (Saunders) for the period 1995-1999 and for Spo doptera litura (Fabricius), Earias vittella (Fabricius) and Bemisia tabaci (Gennadius) in a survey conducted during the 1997-98 cropping season. Of th e 53 field strains of H. armigera, only four were found to exhibit resistan ce to quinalphos, the highest 15-fold, whereas all 16 field strains tested were found to be resistant to monocrotophos. Similarly, out of 40 field str ains tested, only eight were found to express appreciable resistance to met homyl. Resistance in P. gossypiella to quinalphos was high in the majority of the strains tested. Of the seven strains of E. vittella tested, two stra ins from northern India exhibited > 70-fold resistance to monocrotophos. Of the 11 S. litura strains tested, only four were found to exhibit resistanc e factors of 10 to 30-fold to quinalphos and monocrotophos. All of the B. t abaci field strains exhibited resistance to methomyl and monocrotophos and susceptibility to triazophos. Practical implications for pest control resul ting from the observed patterns of cross-resistance between quinalphos, mon ocrotophos and methomyl are discussed.