Toxicity, stage specificity, and sublethal effects of abamectin and several classes of insect growth regulators to Platynota idaeusalis (Lepidoptera: Tortricidae) and Stethorus punctum (Coleoptera: Coccinellidae)

The tufted apple bud moth (TABM), Platynota idaeusalis is the most important direct pest of apple in Pennsylvania and the coccinellid, Stethorus punctum (LeConte), is the main predator of phytophagous mites. Conservation of this predator by the selective use of broad-spectrum insecticides in controlling other orchard pests is the cornerstone of the Pennsylvania integrated pest management (IPM) program. High levels of resistance to organophosphate insecticides by TABM has lead to the increased use of carbamates which disrupt biological control of phytophagous mites by organophosphate tolerant S. punctum. Several classes of insect growth regulators (IGRs) and abamectin were investigated as alternatives to broad-spectrum insecticides.;IGRs and abamectin had significant effects on TABM larval development and reproduction when applied at sublethal concentrations (LC;Fenoxycarb, teflubenzuron, and azinphosmethyl were toxic to S. punctum eggs in laboratory bioassays, while abamectin was toxic to mid-instar larvae and adults. Fenoxycarb reduced S. punctum larval populations in field experiments and both fenoxycarb and teflubenzuron increased mortality in S. punctum pupae. Tebufenozide was the most effective compound tested for controlling TABM in three years of field trials while not affecting S. punctum populations. A single application per TABM brood gave much better control than 3-4 applications/brood of organophosphate insecticides.;Laboratory bioassays with organophosphate resistant and susceptible strains of TABM demonstrated high levels of cross-resistance to diflubenzuron and low levels to hexaflumuron and fenoxycarb. The use of synergists with diflubenzuron and azinphosmethyl indicated esterase enzymes to be important in resistance. Multiple bioassay readings found that mortality from IGRs and abamectin was delayed after initial exposure. Stage specificity trials with TABM showed hexaflumuron to be the only material equally effective on all larval instars. All other compounds tested except fenoxycarb were more effective on early instars than later instars. Azinphosmethyl, fenoxycarb, and hexaflumuron were effective ovicides.