Susceptibility of Leafrollers (Lepidoptera: Tortricidae) from Organic and Conventional Orchards to Azinphosmethyl, Spinosad, and Bacillus thuringiensis

• Published in: Journal of economic entomology 2003-06, Vol.96 (3), p.879-884
• Main Authors: Smirle, Michael J., Lowery, D. Thomas, Zurowski, Cheryl L.
• Format: Article
• Language: English
• Subjects: Animals; apples; azinphos-methyl; Azinphosmethyl - pharmacology; Azinphosmethyl - toxicity; Bacillus thuringiensis; Bacillus thuringiensis - physiology; Biological and medical sciences; Biological control; biopesticides; Chemical control; Choristoneura rosaceana; Control; Drug Combinations; Fundamental and applied biological sciences. Psychology; insect control; insect pests; Insecticide Resistance; INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT; Insecticides - pharmacology; Insecticides - toxicity; leafrollers; Lepidoptera - drug effects; Lepidoptera - microbiology; lethal dose; Macrolides - pharmacology; Macrolides - toxicity; Malus domestica; mortality; orchard pest management; orchards; organic orchards; organic production; Pandemis; Pandemis limitata; pest management; Phytopathology. Animal pests. Plant and forest protection; Protozoa. Invertebrates; spinosad; toxicity; Trees - parasitology
• ISSN: 0022-0493; 1938-291X; 0022-0493
• DOI: 10.1603/0022-0493-96.3.879

Populations of obliquebanded leafroller, Choristoneura rosaceana Harris, and three-lined leafroller, Pandemis limitata Robinson, were obtained from seven sites in the Okanagan and Similkameen Valleys of British Columbia and assayed for their responses to three insecticides using a leaf disk bioassay. Lethal concentration ratios (LCRs) were calculated for all populations compared with a susceptible laboratory colony of C. rosaceana; significant variation was detected in response to all three insecticides. LCRs were 0.86–15.52 for azinphosmethyl, 0.38–2.37 for spinosad (Success), and 0.58–4.89 for Bacillus thuringiensis (Foray). Correlation analysis indicated no cross-resistance among the three insecticides. Leafroller populations obtained from apple orchards managed with organic production practices were more susceptible to azinphosmethyl than leafrollers obtained from conventionally managed sites. Conversely, the highest levels of tolerance to B. thuringiensis were observed in the populations from organic sites, possibly reflecting usage patterns; B. thuringiensis is one of the few insecticides allowed under organic production guidelines. All populations were highly susceptible to spinosad, which may be a useful tool for resistance management programs if used judiciously.