Life history study of multiple clones of insecticide resistant and susceptible greenbug Schizaphis graminum (Homoptera : Aphididae)

Comparative differences and similarities in prereproductive time (d), proge ny production in a time equal to d (M-d), and intrinsic rate of increase (r (m)) were established for one susceptible (S) and three resistant (R) strai ns of the greenbug, Schizaphis graminum (Rondani) reared on sorghum hybrids Dekalb G550E and Cargill 607E. The R strains showed three patterns of elev ated esterase activity. Four R1 clones, four R2 clones, one R3 clone, and f our S clones were evaluated. The interaction of sorghum hybrid and greenbug strain did not significantly influence any of the parameters measured. How ever, R1 greenbugs exhibited a significantly longer prereproductive period than the other strains. In addition, the R1 strain had a significantly slow er intrinsic rate of increase than the R2 or S greenbug strains, but did no t differ significantly from the R3 strain. These results suggest that R1 gr eenbugs may be less fit than the other strains studied.