Stage-specific control of grape berry moth, Endopiza viteana (Clemens) (Lepidoptera: Tortricidae), by selective and broad-spectrum insecticides

The insect growth regulators (IGRs) tebufenozide and methoxyfenozide and the broad-spectrum insecticides azinphosmethyl, carbaryl, and fenpropathrin were compared for their activity against adult, egg, and larval stages of the grape berry moth, Endopiza viteana (Clemens) (Lepidoptera: Tortricidae), under laboratory and vineyard conditions. Adult mortality was not affected by exposure to field-equivalent rates of tebufenozide or methoxyfenozide on grape clusters, whereas all the broad-spectrum compounds significantly reduced adult survival, compared with the untreated controls. Surviving adult moths laid significantly more eggs on berries treated with the IGRs than on berries treated with any of the broad-spectrum insecticides. Survival of these eggs through to late larval and pupal stages was significantly lower on methoxyfenozide-treated grapes than on untreated grapes, and no pupae were found when grapes were treated with azinphosmethyl or fenpropathrin. Neither of the growth regulator insecticides limited egg eclosion or larval development by E. viteana when insecticides were applied before egg laying, whereas broad-spectrum insecticides were effective against both eggs and neonates at this timing. When applied after egg eclosion, all insecticide treatments significantly reduced survival of grape berry moth larvae. Under vineyard conditions, berries with 1-d-old residues of tebufenozide or methoxyfenozide received more E. viteana eggs than berries treated with broad-spectrum compounds. After aging for 7 or 14 d, no significant effects on E. viteana survival were detected among treatments. Whereas broad-spectrum insecticides provide control of multiple life stages of E. viteana, integration of tebufenozide or methoxyfenozide into vineyard management programs for control of this pest will be most successful if applications are timed for egg hatch.     

Resistance and cross-resistance to four insecticides in populations of obliquebanded leafroller (Lepidoptera: Tortricidae)

Populations of obliquebanded leafroller, Choristoneura rosaceana (Harris), were collected from organic and conventionally managed orchards located in the Okanagan and Similkameen Valleys of British Columbia Neonate F1 progeny were assayed for resistance to azinphosmethyl, tebufenozide, methoxyfenozide, and indoxacarb using a leaf disk bioassay. Significant differences in resistance levels among populations were observed for all four insecticides. Insects collected from organic sites were more susceptible to all insecticides than were insects collected from conventional sites. Resistance to the benzoylhydrazine insect growth regulators tebufenozide and methoxyfenozide was highly correlated with resistance to azinphosmethyl across populations, indicating cross-resistance between these compounds. The highest levels of resistance were observed with indoxacarb, but resistance levels to indoxacarb did not correlate with those for azinphosmethyl. Dose-response regression lines for tebufenozide were parallel across populations, suggesting that the resistance mechanism(s) were quantitatively, but not qualitatively, different. Cross-resistance between azinphosmethyl and benzoylhydrazine insecticides indicates that a resistance management strategy for obliquebanded leafroller involving the rotation of these materials is not likely to be successful.     

Synergism of tebufenozide in resistant and susceptible strains of obliquebanded leafroller (Lepidoptera: Tortricidae) and resistance to new insecticides

Cross-resistance of the obliquebanded leafroller, Choristoneura rosaceana (Harris), to tebufenozide was reported from laboratory studies before it had been used in commercial orchards in New York State. Bioassays with obliquebanded leafroller larvae from tebufenozide and organophosphate susceptible and resistant colonies were conducted with chlorfenapyr, emamectin benzoate, fenoxycarb, fipronil, spinosad, and tebufenozide to determine if cross-resistance was present before these new insecticides were introduced into commercial orchards. Resistance ratios ranged from 1.1 to 3.2 for all insecticides except tebufenozide (12.8). Significant differences between susceptible and resistant colonies were found with emamectin benzoate, fenoxycarb, and fipronil. The effect of the metabolic synergists piperonyl butoxide (PBO) and diethyl maleate (DEM) on tebufenozide toxicity was examined to determine mechanisms for obliquebanded leafroller resistance to tebufenozide and potential mechanisms for other new insecticides. At a concentration of 20 ppm, PBO and DEM significantly synergized the toxicity of tebufenozide in resistant and susceptible colonies (three- to fourfold). Obliquebanded leafrollers may be resistant to new insecticides with distinct modes of action even if these compounds have not been previously used in commercial orchards.