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HORTICULTURAL ENTOMOLOGY

Potential New Insecticides for the Control of Western Flower Thrips (Thysanoptera: Thripidae) on Sweet Pepper, Tomato, and Lettuce
S. BROUGHTON1
AND

G. A. HERRON

Department of Agriculture and Food Western Australia, Division of Plant Industries, Baron-Hay Court, South Perth WA 6151 and 1NSW DPI, Elizabeth Macarthur Agricultural Institute, PMB 8, Camden NSW2570, Australia

J. Econ. Entomol. 102(2): 646Ð651 (2009)

ABSTRACT New pesticides are required to maintain effective resistance management strategies for control of western ßower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). We tested the efÞcacy of acetamiprid, and thiamethoxam, two neonicotinoids that represent a newer class of insecticides for the control of thrips.We also tested chlorfenapyr, a pyrrol compound, and a lower than registered rate of the biopesticide spinosad. Laboratory bioassays were used to predict the relative efÞcacy of insecticides against F. occidentalis and to forecast likely Þeld rates. Two doses within the calculated LC99.99 range were used to predict Þeld rates and trial rates of 0.5 g and 1.0 active ingredient (AI)/literacetamiprid, 0.025 and 0.05 g (AI)/liter chlorfenapyr, 0.3 and 0.6 g (AI)/liter thiamethoxam, and 0.01 g (AI)/liter spinosad were tested in the greenhouse against pepper, lettuce, and tomato. With the exception of acetamiprid, Þeld trial doses predicted from laboratory bioassay translated to effective Þeld efÞcacy. All products controlled F. occidentalis at the rates trialed and so have potential to augmentcurrent chemical controls. Increasing mortality correlated with increasing acetamiprid concentration in a greenhouse lettuce trial, suggesting that the higher trial rate (1.0 g [AI]/liter) may be required in some lettuce crops. The lower than registered (0.01 g [AI]/liter) rate of spinosad also signiÞcantly reduced F. occidentalis numbers and is a viable control option that may be useful inspeciÞc integrated pest management programs. The implications of introducing neonicotinoids into existing insecticide resistance management strategies for F. occidentalis are discussed. KEY WORDS thiamethoxam, acetamiprid, chlorfenapyr, spinosad

Western ßower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a key thrips pest of horticultural crops, including Þeld- andgreenhouse-grown vegetables in Australia and many other parts of the world. The reasons for the major pest status of F. occidentalis are four-fold. First, it is highly polyphagous, attacking 240 species from 62 different plant families (Lim et al. 2001). Thus, growers often need to control F. occidentalis, both within the crop and on host weeds within and adjacent to the crop. Second, F. occidentalis isan efÞcient vector of plant viruses, including tomato spotted wilt virus, which affects sweet pepper, eggplant, lettuce, onion, potato, and tomato by causing wilting, lesions, fruit deformation, and subsequent crop loss (Cho et al. 1989). Third, F. occidentalis is difÞcult to control because of its behavior, with adults and larvae hiding and feeding in protected narrow crevices in the ßowers andfoliage (Jensen 2000a). Additionally, prepupae and pupae are often found in the soil or leaf litter, and eggs are laid in fruit, ßower, or leaf tissue, requiring multiple sprays to achieve control (Broughton and Herron 2007). Fourth, F. occidentalis develops insecticide resistance,
1

Corresponding author, e-mail: smbroughton@agric.wa.gov.au.

with populations resistant to organochlorines,organophosphates, carbamates, and pyrethroids reported from greenhouse and Þeld populations in Australia (Herron et al. 1996; Herron and Gullick 2001; Herron and James 2005, 2007), Canada, Kenya, Spain, Switzerland, Israel, and California (reviewed by Jensen 2000a). Cross-resistance, whereby resistance to one insecticide confers resistance to another insecticide to which the insect has not been...
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