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European red mite

Image of European red mite

European red mite (Panonychus ulmi)  is oval, bright red, and has a small stalk arising from the top. It is a major tree fruit pest attacking apples, stone fruits, and pears.

The adult female mites are brick red with white spots at the base of six to eight hairs on their back. The male mite is more slender and lighter in color than the female, with a more pointed abdomen. Eggs are red, globular and somewhat flattened (onion shaped) with a slender stalk on the upper side. European red mites overwinter as eggs laid in roughened bark around the bases of buds and spurs on small branches. During the summer eggs are laid on the underside of leaves. Egg hatch in the spring is closely correlated with bud development and begins close to the tight cluster stage. During the summer, eggs require 7 to 14 days to hatch.

The mites injure the tree by feeding on leaves, destroying chlorophyll, and increasing respiration. This is accomplished by the insertion of the mite's mouth parts into the leaf cells to withdraw the contents. All motile stages feed on the foliage. The lower leaf surface is preferred, but both leaf surfaces are attacked when populations are high. All apple varieties are susceptible to attack, but the mites appear to increase faster and to higher densities on 'Delicious' and 'Yorking'. A characteristic brown foliage, starting as a subtle cast to the green leaf, but in severe cases becomes bronze, results from heavy mite feeding. The most serious injury occurs in late spring and early summer when trees are producing fruit buds for the following season. Moderate to heavily injured trees (i.e. with 750 mite days or with 43 motile mites per leaf) produce fewer and less vigorous fruit buds. Mites feeding on leaves also reduce their ability to manufacture enough photosynthates for desirable sizing of fruit. Injury effects from mite feeding are more severe during periods of drought stress. Late season high populations of mites can cause further indirect loss of fruit by depositing overwintering eggs, especially in the calyx end.