Field Characteristics of Fruit-Tree-Attacking Spider Mites in the Pacific Northwest

John Mellott

Mite

Egg

Summer adult

Stage and location of overwintering form

Degree of webbing

Comments

Clover mite

Bryobia praetiosa

Red, spherical, and smooth

Dark brown to greenish, flattened mite with front legs of female much longer than other legs. Posterior marginal setae are drop-shaped on the adult female.

Overwinter as larvae (red), nymphs (red-green), and adults (red-green) in soil, litter, and on bark of trees. The larva has slender dorsal setae.

Very little

Not too numerous on fruit trees. May migrate into homes in spring and fall. Often confused with B. rubrioculus.

Brown mite

Bryobia rubrioculus

Red, spherical, and smooth

Similar to B. praetiosa, but the posterior setae are fan-shaped.

Overwinter as eggs on twigs and branches. Larvae, nymphs, and adults may be found in litter and on bark of trees. The larva has fan-shaped dorsal setae but otherwise looks much like that of B. praetiosa.

Very little

Found primarily on trees and shrubs and may be quite abundant in orchards.

European red mite

Panonychus ulmi

Red, slightly flattened, with a dorsal stalk

Female a brick-red color with obvious white tubercles on the dorsal surface of the body from which hairs arise.

Overwinter as red eggs on twigs and branches.

Very little

Feed heavily on wild rose bushes; wild rose can be a source of infestation if orchard boundaries are not sprayed.

Yellow spider mite

Eotetranychus carpini borealis

Translucent, spherical

Pale yellow, with 2 or 3 paired fields of small dark spots on body. The adults are smaller than the adults of Tetranychus urticae. Both species may be on same leaf.

Overwinter as yellow females on trees and , in ground litter.

Very little

Usually present in small colonies on leaves.

McDaniel spider mite

Tetranychus mcdanieli

Whitish (appears pale green on leaf) and spherical.

Greenish to yellowish with two small dark spots near middle of body and two larger spots near posterior

Orange females overwinter on trees or in ground litter.

Extensive

May be a serious problem on fruit at harvest time.

Twospotted spider mite

Tetranychus urticae

Whitish (appears pale green on leaf) and spherical.

Greenish to yellowish with two large, dark spots on body; Body globular.

Overwinter as orange females on trees or in ground litter. Orange females may be found as early as mid-August.

Extensive

Feed most commonly on undersides of leaves.