Greenhouse and field evaluation of six novel insecticides against the greenhouse whitefly Trialeurodes vaporariorum on strawberries

The efficacy of six novel insecticides against the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), on strawberries was evaluated in greenhouse and field experiments. Soil applied imidacloprid at 10, 20 and 40 mg per plant caused adult mortalities of 82%, 93% and 96%, respectively, at 48 h post-treatment in the greenhouse. A significant residual activity resulted in 84-87% mortality after 40 days and 58-78% mortality after 60 days. Topical applications of pyriproxyfen at rates of 16-65 microgram AI/ml completely inhibited egg hatch, whereas lower rates of 0.05-0.20 microgram AI/ml resulted in 38-70% egg hatch. However, most nymphs that hatched failed to develop into adults. Using 0.5, 1.0 and 2 x their greatest label concentration applications of buprofezin and pyridaben caused 100% mortality of nymphs whereas pymetrozine caused only 70%, 74% and 78%, mortality respectively. Thiamethoxam at 0.5 and 1.0 x its greatest label concentration killed 67% and 90% of nymphs, respectively. In field experiments, imidacloprid applications decreased adult densities by 31-61% from 21 to 42 days post treatment compared with controls, and suppressed densities of third and fourth instars by 34-68% after 42 days of treatment. Pyriproxyfen and buprofezin did not significantly affect adult densities on most sampling dates. An application of buprofezin followed by an application of pyriproxifen decreased nymphal densities by 98% on the sampling dates of 4 and 11 May and maintained 61-85% control after the sampling on 1 June. Applications of pyriproxyfen followed by buprofezin had no effect on the nymphal densities on 4 and 11 May but densities had fallen by 78-90% from early to late June. Applications of pyridaben and pymetrozine had no effect on adult densities on any sampling dates. However, pyridaben suppressed densities of third and fourth instars by 39-44% on 4 and 11 May sampling dates, and by 47-73% in late June. Pymetrozine had no effect on the densities of nymphs. Applications of thiamethoxam had no effect on adult densities on most sampling dates and did not significantly change the immature densities compared to the control. The potential roles of these insecticides in integrated greenhouse whitefly management programs are discussed.