Mites That Attack Grapes

European Red Mite, Panonychus ulmi (Koch)

Description and Life Cycle

The European red mite causes considerable damage to apples in some orchards, it also becomes a problem in vineyards from time to time.

The adult female of the European red mite is dark red to reddish-brown, has eight legs and is about 1/50 inch long. Adult male mites are smaller than females and have a pointed abdomen; they are usually dull green to brown. Eggs, which are globe-shaped and red, are laid on the undersides of leaves in the summer. The eggs are tiny and require a magnifying glass to be seen. During late summer and early fall, eggs are laid around cane nodes, where they overwinter, several generations occur each season.

Damage Symptoms

The adults and nymphs of this species feed on the undersurfaces of leaves, and in heavy infestations, the leaves turn a bronze color. If bronzing occurs early enough in the season, a negative effect on fruit ripening may occur as feeding may interfere with the normal photosynthetic process of the leaves.

Management

Growers should apply miticide sprays before bronzing occurs. In some vineyards, this pest is kept at low levels by naturally occurring predatory mites and predaceous insects.

Monitoring

Monitoring for European red mite can be accomplished by looking at the underside of the leaves for their presence at the same time you are scouting your vineyard for leafhoppers and grape berry moth. You may also keep a close eye out for bronzing while traveling through the vineyard on your tractor. This can be done at the same time your applying fungicide sprays to your vineyard.

Fortunately, predaceous mites on grapes show considerable resistance to a number of organic pesticides, in particular the organic phosphates. Some chemicals reduce leafhopper and/or spider mite populations while allowing predaceous mites to maintain control of the latter. Ideally , treatments should be applied so that mites are reduced below economic levels without killing predaceous mites or reducing their food source to the extent that they starve.

The grape erineum mite is very different in appearance from the twospotted spider mite. It is tiny-about 1/250 inch long-worm-like and yellow. The erineum mite overwinters under the bark of 1-year-old grape canes and crawls out onto the leaves during the summer to feed and reproduce. Several generations occur every year.

The damage due to grape erineum mite is noticeable. On the upper leaf surface, a gall-like or blister-like erineum forms, and on the lower surface, a white, dense growth of abnormally curled plant hairs occurs. The mites feed and reproduce within the whitish plant growth on the undersurfaces of the foliage.

In situations where severe infestations become established, reduced vigor and impaired vine growth could result from feeding by the mites on the new leaves. The mites may be introduced into a vineyard on infested nursery stock.

In many respects, the two-spotted spider mite is similar to the European red mite. The injury it causes to grapes is similar to that attributed to the European red mite but differs in that there is much silken webbing where populations are high.

he adult female is less than 1/50 inch in length and varies in its coloration, individuals being shades of green, yellow or red. Two darker, dorsal pigmented spots give this mite its common name. Male mites are more active and smaller, and have a more narrow,. pointed abdomen than females. Tiny eggs, clear to pale green and spherical! are laid on the undersides of leaves, where feeding and web spinning occurs.

Hot, dry weather conditions favor the development and proliferation of spider mites; on the other hand, low temperature, high humidity and moist situations are deleterious to survival. The two-spotted spider mite overwinters as orange females under grape bark. There are many overlapping generations every year.