Reproduction and Mortality of the Two-Spotted Spider Mite on Fruit Seedlings Treated with Chemicals1

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Abstract
Plants deficient in nitrogen and phosphorus were less favorable than normal plants for the two-spotted spider mite, Tetranychus urticae (Koch), but were more severaly damaged by the mite increases. Added amounts of nitrogen, phosphorus, and potassium in the soil, and various foliar nutrients did not appreciably affect the mites. Also, various fungicidal sprays and heavy residues of insecticide and fungicides in the soil had no marked effects on egg laying or mortality of the mites on peach seedlings. Egg laying was greatly suppressed by the antibiotic fungicide cyclohexamide. Carbaryl and DDT did not stimulate egg laying; therefore such applications do not account for increases in mite populations observed to follow orchard treatments with these materials. Carbaryl had no appreciable effect on mortality of the two-spotted spider mite, but was very toxic to its important predator, Typhlodromus sp.