Sf. Abdelghafar et al., PYRETHROID RESISTANCE IN 2 FIELD STRAINS OF HELICOVERPA-ZEA (LEPIDOPTERA, NOCTUIDAE), Journal of economic entomology, 86(6), 1993, pp. 1651-1655
Topical toxicities of three pyrethroids (permethrin, cypermethrin, and
fenvalerate), one carbamate (carbaryl), and one organophosphate (meth
yl parathion) were determined with third instars of two Helicoverpa ze
a (Boddie) strains that were established from field collections in com
and cotton where-control difficulties with pyrethroids were experienc
ed. The data were compared with those of an insecticide-susceptible la
boratory strain. Resistance ratios (RR at LD50 and LD90) indicated tha
t Illinois-strain larvae were resistant to permethrin (5.2- and 10.8-f
old), cypermethrin (3.0- and 18.0-fold), and carbaryl (2.6- and 2.7-fo
ld), whereas Arkansas-strain larvae were resistant to permethrin (5.7-
and 8.8-fold), cypermethrin (5.0- and 10.0-fold), fenvalerate (2.2- a
nd 2.7-fold), methyl parathion (3.2- and 3.2-fold), and carbaryl (3.1-
and 1.9-fold). Results of studies of the effect of synergists on toxi
city of cypermethrin to larvae of the Arkansas strain were inconclusiv
e; however, they suggested that both metabolic and nonmetabolic (targe
t site) resistance mechanisms could be involved.