Chemical residues and bioactivity of tebufenozide applied to apple foliage |
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Authors: | Smirle Michael J Lowery D Thomas Zurowski Cheryl L |
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Affiliation: | Agriculture & Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, BC VOH 1ZO, Canada. smirlem@agr.gc.ca |
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Abstract: | Tebufenozide, an insect growth regulator that acts as an ecdysone agonist, was applied at recommended label rate to apple trees in August 1997 and May 1998. Foliar residues were determined by high-performance liquid chromatography from samples collected 2, 24, 48 and 96 h post-spray, and at weekly intervals thereafter for 9 weeks in 1997 and 11 weeks in 1998. Foliage sampled at the same times was used in bioassays to determine residual toxicity to first-instar obliquebanded leafrollers, Choristoneura rosaceana (Harris). Residue decay followed first-order kinetics in both years, with residual half-life of 36.3 days in 1997 and 7.2 days in 1998. Estimates of the time needed to reduce bioactivity to 50% in bioassays were 18.7 days in 1997 and 36.3 days in 1998. The accuracy of equations describing decay of tebufenozide residues and bioactivity over time was not improved by using degree-day accumulations as the independent variable. |
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Keywords: | tebufenozide residues Choristoneura rosaceana apple pest management degree‐day models |
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