San Jose Scale on Apple
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San Jose scale (Quadraspidiotus perniciosus) is minute (1/20 of an inch), flattened, gray, circular with concentric rings, and a tiny knob in the center. Crawlers are yellow, only 1/200 inch in size, resemble spider mites in shape and are visible only with a hand lens. Red flecking on fruit at harvest or under bark on new growth (caused by toxic saliva injections) are indications of San Jose scale infestation.
San Jose scale damage to fruit.
(Photo: Ricardo Bessin, University of Kentucky)
San Jose scale on branch.
(Photo: Ricardo Bessin, University of Kentucky)
San Jose scale injury under bark.
(Photo: Ricardo Bessin, University of Kentucky)
Management:
- Scouting
- Dormant oil applications
- Spring insecticide spray (either at pre-bloom or early summer targeting the crawler stage)
- Use a piece of black tape (sticky side out) on an infested limb to detect crawlers
