Apple Rust Mite Apple Rust Mite Apple rust mite, Aculus schlectendali , is commonly found, but rarely a pest of apple in Pennsylvania. It is usually controlled by natural predators or pesticide sprays applied against other pests such as diazinon, Vendex, or Vydate. However, rust mite populations can build to injurious levels in some situations. Examination of the leaf midrib with a strong hand lens is usually needed to verify mite presence.
Apple rust mites overwinter as an adult females under the bud scales of apple trees.
At budbreak they become active and feed and reproduce until July or early August when overwintering females are produced. In low numbers, apple rust mites are considered beneficial in that they provide an alternate food source for the predators of European red mites and twospotted spider mites. These mites feed on the underside of the leaf, usually causing little if any damage. Under some conditions mite populations may expand, and their feeding can cause the leaf to take on a silvery appearance as leaf cells are destroyed and chlorophyll is lost. Silvering symptoms do not appear until mite populations build beyond 200 mites per leaf.