Many laboratory studies have shown reproductive disadvantages in development time and fecundity for insecticide-resistant arthropods. Polyacrylamide gel electrophoresis, surface residue bioassays, and petri dish bioassays have been used to document the existence of 2 esterase-mediated resistance strains in greenbugs. Resistant greenbugs have been catego-rized as pattern 1 or pattern 2 strains based on general esterase banding patterns. This report documents a life history study of an insecticide-susceptible and 2 insecticide-resistant strains of greenbug, Schizaphis graminum (Rondani), reared on a susceptible and a resistant sorghum hybrid. Intrinsic rate of increase was affected significantly by greenbug strain. The pattern 1 resistant strain had a slower intrinsic rate of increase than the susceptible and pattern 2 resistant strains. The interaction of sorghum hybrid and green bug strain had a significant effect on the effective fecundity. The pattern 1 strain produced fewer offspring on the resistant hybrid than did the pattern 2 strain. The pattern 2 strain produced fewer offspring on the susceptible hybrid than the insecticide-susceptible strain. More offspring were produced by the pattern 1 strain on the susceptible hybrid than on the resistant hybrid. The green bug strain alone did not affect prereproductive period, effective fecundity, total fecundity, total reproductive period, and lifespan of insecticide-resistant and insecticide-susceptible greenbugs. Because the most prevalent insecticide-resistant greenbugs, pattern 2, appear to have no life history disadvantages, strict insecticide use management should be used to prevent resistance from spreading.
Document Type: Research Article
Publication date: December 1, 1997
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