When insecticide spraying ceases prematurely Tetranychus urticae mites are not killed by predators, they wither and die in situ

Abstract

An outbreak of spider mites on apple trees sprayed with insecticide collapsed when spraying was stopped prematurely. But mites were not taken by predators. They remained at their feeding site but became torpid, withered and died. This observation supports earlier evidence that mites increase because the application of insecticide caused protein in the leaves to break down releasing soluble amino acids into the sap. This improved the nutrition of the mites, allowing them to increase. But when spraying was stopped at the height of an outbreak this flow of amino acids ceased and the mites starved from the consequent decline in their nitrogen nutrition.