Single applications of 9 insecticides were made to apple trees in mid-August and the relative population densities of the European red mite, Panonychus ulmi (Koch), and predaceous mite, TyphlodromlLs (A.) fallacis (Garman), were measured over a period of 5 weeks. P. ulmi increased in abundance following applications of carbaryl, NIA-10242 2,3-dihydro-2,2-dimethyl-7-benzofuranylmethylcarbamate), dioxathion, GS-13005 (O,O-dimethyl phosphorodithioate S-ester with 4-(mercaptomethyl)-2-methoxy-2 -1,3,4-thiadiazolin-5-one), ethion, and carbophenothion. Populations declined on trees treated with azinphosmethyl, Imidan® (O,O-dimethyl S-phthalimidomethyl phosphorodithioate), diazinon, and on the control trees. The 3 last-mentioned insecticides were the least toxic to T. fallacis. In general, there was an inverse relationship between the toxicity of the insecticides to the predator and changes in P. ulmi populations. Evaluation of the data suggested that a major factor accounting for changes in P. ulmi densities was the toxicity of the insecticides to T. fallacis, rather than the effect of the insecticides on P. ulmi per se.
Document Type: Research Article
Publication date: December 16, 1968
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