Evaluation of tebufenozide carry-over and residual effects on spruce budworm (Lepidoptera: Tortricidae)

Laboratory and field studies investigated carry-over effects of tebufenozide on spruce budworm, Choristoneura fumiferana (Clemens). In the laboratory, third and fourth instars were fed either sublethal doses of tebufenozide (10 ppm) or water on Abies balsamea (L.) Mill. needles, reared to adulthood and allowed to oviposit on laying surfaces 1 or 14 d after being sprayed with water or tebufenozide concentrations of 17.5, 35.0, and 70.0 g/ liter. Percentage adult emergence and sex ratio were not affected by larval ingestion of the tebufenozide. Also, the mean number of eggs laid on untreated wax paper by moths reared from tebufenozide-treated larvae was similar to the controls. Hence, tebufenozide did not inhibit carry-over effects on treated larvae. Oviposition on tebufenozide-treated wax paper by moths reared from untreated larvae was affected by both the substrate concentration and the age of the treatment residue. When offered treated and untreated laying surfaces simultaneously, C. fumiferana did not show a preference. However, significantly fewer eggs were laid on both laying surfaces by fewer females than when tebufenozide was absent. Residual tebufenozide on wax paper did not affect egg hatch but topical applications were toxic to eggs. Field studies appear to corroborate laboratory results and suggest that although the ingestion of tebufenozide by larval spruce budworm might not impair adult reproduction, the insecticide's presence in the environment could inhibit oviposition. This inhibition was considered to be a primary factor in tebufenozide's multi-year effects against spruce budworm populations.