Stage Specificity of Various Insecticides to Tufted Apple Bud Moth Larvae (Lepidoptera: Tortricidae)

The stage specificity of azinphosmethyl, abamectin, fenoxycarb, hexaflumuron, and tebufenozide was determined through diet incorporation on the neonate, 3rd, and 5th instars of a pesticide-susceptible laboratory strain of the tufted apple bud moth, Platynota idaeusalis (Walker) Mortality was determined 7 and 14 d after initial exposure and at adult eclosion Ovicidal activity with these same compounds and diflubenzuron was determined with topical applications to freshly laid eggs (<24 h). Although the mortality of the different larval stages did not increase significantly after 7 d with azinphosmethyl, the LC₅₀s of the 3rd and 5th instars were 90 and 110 times higher than those of the neonates. Mortality with all other compounds tested increased after the initial 7-d reading. Abamectin was very stage specific to neonate larvae during the initial mortality readings (130-170 times), but delayed mortality in the later instars increased with time, so that by adult eclosion stage, specificity was reduced to 3-8 times. Stage specificity of hexaflumuron and tebufenozide was relatively low across larval instars, but fenoxycarb was ineffective on neonates and 200 times more effective on 5th than on 3rd instars. Azinphosmethyl, hexaflumuron, and fenoxycarb were the most ovicidal compounds tested.