Prunus rust mite (Aculus fockeui)
Pest description and crop damage Adult mites are extremely small and require at least a 10X magnifying lens to scout for them. They are light-color, cylindrical and wedge-shaped. Immature mites are similar in appearance, but smaller and often lighter in color. These mites have piercing-sucking mouthparts and feed on the outermost plant cells. Eriophyid mite feeding can cause a silvering or bronzing of leaf foliage, and heavy infestations may lead to premature defoliation.
Biology and life history These mites overwinter as diapausing females in buds immediately under the bud scales, or in cracks along the bark. As buds expand in the spring, females leave their overwintering sites and begin feeding, then after a few days lay eggs. In the spring, eggs may take two weeks to hatch, but by midsummer they may hatch in as little as 3 to 4 days. There are several generations per year. As the foliage deteriorates in late summer, diapausing females are produced.
Pest monitoring Typically when crop damage by these mites is detected, the best plan is to monitor and manage this pest the following spring. Observe the leaves for signs of mite feeding and use a hand lens to check for the mites, particularly in fruit trees with a history of eriophyid mite infestations.
Phytoseiid predator mites almost always keep these mites under control when broad-spectrum insecticide applications are avoided. Rust mites form a significant food source for these predator mites that also control spider mite pests, so early-season populations of this eriophyid mite should be tolerated. Hot, dry weather and the hardening off of leaves can reduce eriophyid mite numbers.
Successive sampling during the dormant, delayed-dormant period or early spring can best target pesticide applications towards active and growing populations of eriophyid mites before mite damage causes leaf bronzing or silvering. Do not apply these products after the damage has been done.
Management-chemical control: HOME USE
Apply sprays using enough water to cover the tree thoroughly, including small limbs. Apply during the dormant, delayed-dormant period.
- horticultural mineral oil-Some formulations OMRI-listed for organic use.
- carbaryl-Highly toxic to bees.
Management-chemical control: COMMERCIAL USE
Spring and summer sprays
- spirodiclofen (Envidor 2SC) at 16 to 18 fl oz/A. REI 12 hr. PHI 7 days. Limited to one application per season.