Chemical control of Western Flower Thrips (Frankliniella occidentalis Pergande)

Fifty-one pesticides currently registered for use in the UK were tested in the laboratory against Western Flower Thrips (Frankliniella occidentalis) maintained on chrysanthemum leaf discs. In an initial screening trial of the pesticides against larval thrips, 14 caused more than 75% mortality three days after exposure. These were tested further against adults and pupae and retested against larvae. A series of glasshouse trials were conducted using the most efficacious pesticides evaluated earlier. Granular and systemic compounds were included in the glasshouse trials since these could not be evaluated satisfactorily in the laboratory. Malathion proved to be the most potent chemical currently registered for control of thrips on a wide range of horticultural crops.