Effects of Pyrethroid Insecticides on Eggs and Larvae of Resistant and Susceptible Populations of Spotted Tentiform Leafminer

Abstract Resistance to pyrethroid insecticides, identified previously in adults of Phyllonorycter blancardella (Fabr.), was shown to extend to both egg and larval stages. Eggs of both resistant and susceptible strains were more susceptible than larvae to various pyrethroid insecticides. Eggs treated 0–2 days post oviposition were more susceptible than 4- to 6-day-old eggs and/or larvae for both strains. Older larvae, especially from resistant strains, were less susceptible than early instars. For eggs and 1st-instar larvae, differences between resistant and susceptible strains were largely overcome by treatment with higher concentrations of permethrin. In the field, low levels of resistance were overcome by applications of permethrin at 212.5 g AI/ha diluted in 3370 L water/ha timed for first hatch of eggs.