Baseline toxicity of several pesticides to Hyaliodes vitripennis (Say) (Hemiptera : Miridae)

Hyaliodes vitripennis (Say) is a univoltine indigenous predacious mirid. It has been reported in several orchards where IPM programmes are used. It is a generalist, and feeds on phytophagous mites in addition to other arthrop ods. In Quebec, a foliar application of imidacloprid, deltamethrin or lambd a-cyhalothrin is used at least once per season to manage arthropod pests su ch as leafhoppers and leaf-eating caterpillars. Meanwhile, several applicat ions of metiram, flusilazole, myclobutanil and mancozeb are made to control apple scab [ Venturia inaequalis (Cooke) Winter]. In laboratory trials, co mparison of lethal concentrations of the three insecticides against H vitri pennis nymphs and adults showed no significant difference. However, when le thal concentrations were compared between two growth stages for each insect icide, a significant difference was noted between adults and nymphs treated with lambda-cyhalothrin, adults being more susceptible than nymphs. No suc h difference could be detected for imidacloprid or deltamethrin. When LC50 values were compared with the manufacturer's label rates, deltamethrin and imidacloprid were toxic to the nymphs and adults, and lambda-cyhalothrin wa s slightly toxic to the nymphs and moderately toxic to the adults. Among th e fungicides evaluated in the laboratory, myclobutanil showed moderate toxi city to adults at the manufacturer's label rate. The remaining fungicides h ad no toxic effects to adults or nymphs, even at four times the manufacture r's label rate. (C) 2001 Society of Chemical Industry.