European red spider mite (Panonychus ulmi)
Twospotted spider mite (Tetranychus urticae)
Brown mite (Bryobia rubrioculus)
McDaniel spider mite (Tetranychus mcdanieli)
Yellow spider mite (Eotetranychus carpini borealis)
For mite identification, see:
Field Characteristics of Fruit-Tree-Attacking Spider Mites in the Pacific Northwest
Pest description and crop damage All adult spider mites are small, usually only about 0.02 inch long and have eight legs. The various apple-infesting species vary in appearance as follows:
Brown mite: The adult female is dull reddish brown with dark orange markings, and somewhat flattened. The front legs are very long, over twice the length of the other legs, and extend forward from the body.
European red spider mite: Adults are globular, reddish with white spines. Immature mites are similar in appearance, only smaller. Eggs are red and globular.
Twospotted and McDaniel spider mite: Adults are yellowish-brown, about 0.02 inch long. Twospotted mites have two dark spots on the body, while McDaniel mites have four. Immature mites are similar in appearance, only smaller. Eggs are round and translucent to opaque.
Yellow spider mite: Adult females are pale yellow to white with 2 or 3 dark, rectangular markings on each side of the abdomen. Immature mites are similar in appearance to the twospotted spider mite, but have more of a yellowish color. Eggs are clear and spherical.
These spider mites damage tissues by puncturing individual plant cells, then sucking the contents out of the cell. The damage appears as small yellow-white spots on the upper leaf surface. In heavy infestations, the spots coalesce and the leaf yellows or bronzes.
Biology and life history Twospotted, McDaniel and yellow spider mites overwinter as fertilized females under bark or in soil debris. European red mite and brown mites overwinter as eggs in crevices of twig bark and young limbs. They move to young foliage when buds break in spring and produce many generations during spring to autumn. Females can lay up to 10 eggs per day and more than 200 during their lifetime. Egg-to-adult development can occur in 7 to 10 days during summer. Spider mites thrive under hot, dry conditions. Large colonies of mites produce webbing along leaf midrib. Mite dispersal occurs mainly through wind transport.
Pest monitoring Periodically, scout fruit trees for the presence of stippled or yellowing leaves as mite damage can be easier to detect than the mites themselves. Observe the underside of leaves, particularly along the leaf midrib, for mites, mite eggs and webbing and check for the number of pest and predator mites. Sufficient control usually is achieved by midsummer by natural enemies if broad-spectrum insecticide application are avoided.
Spider mite populations are reduced by cool, wet conditions early in the season. Considerable natural control is provided by lady beetles (Stethorus spp.) and minute pirate bugs (Orius spp.). Predator mites such as Typhlodromus spp. or Neoseiulus fallacis are also effective at managing populations of spider mites and can be purchased to augment populations. Avoid pyrethroid sprays during the growing season.
Spider mite infestations are favored by dry, dusty conditions, so avoid creating these problems and stressing the plants. The use of cover crops also reduces dust and mite problems. However, broadleaf weeds like mallow, bindweed, white clover, and knotweed actually enhance mite numbers. Suppression of these weeds with cultivation or grasses may reduce mite numbers. Mites may be washed from the tree with a strong stream of water. Water trees properly, as drought-stressed trees are more susceptible. Avoid excessive nitrogen applications, as this encourages mites.
Management-chemical control: HOME USE
Note: Spider mites can rapidly develop resistance to chemical controls.
- horticultural mineral oil (European red mite only)-Some formulations are OMRI-listed for organic use.
- azadirachtin (neem extract)-Some formulations are OMRI-listed for organic use.
- horticultural mineral oil-Some formulations OMRI-listed for organic use.
- insecticidal soap-Avoid spraying when blossoms are present. Complete coverage, especially undersides of leaves, is essential. Not recommended for use on yellow-skin nectarine varieties. Some formulations are OMRI-listed for organic use.
- plant-derived essential oils-Some have shown efficacy against spider mites. Some formulations are OMRI-listed for organic use.
- pyrethrins-Some formulations are OMRI-listed for organic use.
- spinosad-Some formulations are OMRI-listed for organic use
- sulfur-Some formulations are OMRI-listed for organic use.
Management-chemical control: COMMERCIAL USE
Dormant to delayed-dormant spray
- horticultural mineral oil-Rates vary; check product label. REI varies; check product label.
Spring and summer sprays
- bifenazate (Acramite 50WS) at 0.75 to 1 lb/A. REI 12 hr. PHI 3 days. Do not exceed one application per season. Primarily active towards the motile stages of mites, but has some ovicidal activity.
- clofentezine (Apollo SC) at 4 to 8 oz/A. REI 12 hr. PHI 21 days. Apply only once per season and at first sign of egg deposition. Clofentezine and hexythiazox are primarily mite ovicides and will not control adult mites.
- fenbutatin-oxide (Vendex 50WP) at 1 to 2 lb/A. REI 48 hr. PHI 14 days. Do not exceed two applications or 3 lb/A per season. Apply when mites first appear.
- hexythiazox (Savey 50DF) at 3 to 6 oz/A. REI 12 hr. PHI 28 days. Apply only once per season and at first sign of egg deposition. Hexythiazox and clofentezine are primarily mite ovicides and will not control adult mites.
- spirodiclofen (Envidor 2SC) at 16 to 18 fl oz/A. REI 12 hr. PHI 7 days. Only one application per crop season. Apply when mites first appear.
Resistance management Spider mites can rapidly develop resistance to chemical controls. Clofentezine and hexythiozox have a similar mode of action and should not be applied to the same crop In any one year.