THE INFLUENCE OF SPRAY PROGRAMS ON THE FAUNA OF APPLE ORCHARDS IN NOVA SCOTIA: XVIII. PREDATOR AND PREY POPULATIONS IN RELATION TO MITICIDES

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Abstract
Ovex, tetradifon, and chlorbenside which are largely innocuous, and parathion which is more harmful, to beneficial insects and predaceous mites, have been used in apple orchards in Nova Scotia to control outbreaks of phytophagous mites. Dicofol is used at present but it is toxic to predaceous mites. Animert V-101 is effective against Panonychus ulmi (Koch) but is ineffective on most beneficial species. Dicofol and Animert V-101 initially reduced a high population of P. ulmi but were equally ineffective on predaceous insects. The latter chemical was innocuous to Typhlodromus pyri Scheuten and Vasates schlechtendali (Nal.) but gave partial control of P. ulmi. A similar high population of P. ulmi was reduced to a low level on a comparative untreated plot where a high number of predators was present. This reduction was evident 1 month later than on the treated plots. The overwintering numbers of P. ulmi in 1966 were below a commercially tolerable level on the three plots.