"Field populations of Choristoneura rosaceana (Harris) were collected from commercial apple and cherry orchards in western Michigan. A baseline toxicity study, using a diet overlay bioassay, of eight insecticides was conducted on 12-24h old larvae of the C. rosaceana populations. The commercial cherry population showed resistance to bifenthrin, spinetoram, emamectin benzoate, and indoxacarb with 4.9, 4.1, 5.8, and 21-fold resistance respectively. The commercial cherry population was not resistant to phosmet, methomyl, chlorantraniliprole, and novaluron. The commercial apple population showed resistance to phosmet, bifenthrin, spinetoram, emamectin benzoate, chlorantraniliprole, and indoxacard with 5, 5, 4.3, 6.3, 4.7, and 620.4-fold resistance respectively. The commercial apple population was not resistant to methomyl and novaluron. This difference in resistance levels between the apple and cherry populations is worthwhile and requires further study to identify the source of this difference. Synergism and metabolic studies were conducted to identify the detoxification mechanism against indoxacarb in the tested C. rosaceana field populations. In the diet incorporation bioassay, in both susceptible and cherry populations, only DEF significantly synergized indoxacarb with a synergism ratio (SR) of 6.5 and 22.6-folds respectively. In the apple population all synergists PBO, DEM, and DEF significantly synergized indoxacarb with SR of 9.6, 7.7, and 285.6-folds respectively indicating a complex resistance case with the possible involvement of all three metabolic resistance mechanisms. In the in vitro metabolic study, indoxacarb (DPX-JW062) was very rapidly bio-transformed within 5 min into small molecules in the lower portion of the metabolic pathway when it reacted with the 12,000g midgut supernatant of each population. In the second part of the in vitro study, the bio-transformation of DPX-JW062 remarkably was decreased when it reacted with the pre-inhibited (by DEF) 12,000g midgut supernatant of each population. Additionally, the degradation of metabolites in the upper portion of the metabolic pathway remarkably decreased, which resulted in accumulation of DCJW and MP819 metabolites. The accumulation of DCJW metabolite treatment provided a persuasive explanation of the synergistic impact of esterase inhibitor DEF on indoxacarb toxicity in C. rosaceana. Field-based residual bioassay and residue analysis were conducted to assess the field performance and toxicity longevity of the insecticides that had previously been associated with significant resistance levels in the baseline study. 12-24h old larvae of C. rosaceana were exposed to the leaf samples that were collected at different post-application (DPA) intervals. In apple and cherry trials, the order of residual longevity of insecticides that effectively controlled the tested populations was: bifenthrin and spinetoram (apple: 14, cherry 21 DPA), phosmet (apple: 7, cherry 14 DPA), chlorantraniliprole (apple: 7 DPA), and indoxacarb and emamectin benzoate (apple: 1, cherry 7 DPA). The previously documented significant resistance levels in the tested populations resulted in a measurable loss of field performance only in the cases of emamectin benzoate, chlorantraniliprole, and indoxacarb at 7, 21, and all DPA intervals respectively in the apple trials while in cherry trial just indoxacarb at 7 DPA. In term of long lasting residues, only chlorantraniliprole and indoxacarb maintained measurable leaf residues over all DPA intervals. These findings can help fruit growers make adjustments to spray/re-spray intervals and optimally utilize important chemical tools in their control programs."--Pages ii-iii.
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