Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) chemical control: residues associated with the three consecutive spray strategy
Chemical control of western flower thrips Frankliniella occidentalis requires three consecutive applications of the same pesticide, 3–6 days apart. Initially, pesticides recommended for western flower thrips control were based on established maximum residue limits (MRLs) from previously established use on pests other than F. occidentalis, rather than product efficacy against F. occidentalis. Moreover, MRLs were based on a single application rather than three consecutive sprays. Chemical residues associated with the three-spray strategy were not quantified. Here those residues are quantified and the scope for rate increases is further tested, as laboratory bioassays suggest that some current permit rates may be too low to be effective. At established withholding periods (WHPs), current permit rate applications of abamectin (0.018 g/L) on strawberry and tomato, and methidathion (0.5 g/L) and endosulfan (0.666 g/L) on lettuce produced residues above the current Australian MRL. Results indicated that a higher than the current permit rate for endosulfan (2.0 g/L) could be sustained on cucumber and strawberry at established WHPs, but would require an extension to the current WHP. Similarly, a modest increase in methidathion (1.0 g/L) rate on tomato could be practical, again with a WHP extension. In each instance additional supporting data are required to accurately quantify the proposed WHP extensions.
Document Type: Research Article
Affiliations: 1: New South Wales Department of Primary Industries, EMAI, PMB 8, Camden, NSW 2570, Australia. 2: Department of Agriculture and Food Western Australia, 3 Baron-Hay Court, South Perth, WA 6151, Australia. 3: The University of Sydney, Agriculture, Sydney, NSW 2006, Australia.
Publication date: May 1, 2007