|University of Kentucky Entomology|
SAN JOSE SCALE
by Ric Bessin, Extension Entomologist
University of Kentucky College of Agriculture
San Jose Scale overwinter as immature scales. In the spring, the tiny winged males emerge and mate with the wingless females, and about one month after the begin of the male flight, the first crawlers can be seen.
A few days after settling down, crawlers will secrete a waxy covering over their body that will protect them from pesticides. From this point on female scales will not move. Males will remain in one location until maturity, at which time the winged males will seek out females and the cycle will begin again.
Pheromone Trapping & Degree Day Accumulation
Detecting Crawler Movement
Crawler movement begins sometime between mid-May and mid-June. Dark double-sided sticky tape should be used to monitor for emerging crawlers. A small amount of tape is applied tightly around a scaffold limb after removing surface debris with sandpaper. A limb with a known infestation should be selected. Crawlers will appear as extremely small flattened yellowish insects which can be seen with a hand lens on the tape (especially around the edges). Within two days, the crawlers will find a permanent resting spot where they will feed and begin to secrete a protective waxy covering. There are two generations each year.
Effective control of San Jose Scale in apples is obtained with dormant oil sprays and a late spring insecticide spray aimed at the immature crawler, stage. Sprays directed against crawlers also protect fruit from infestation. Sprays should be timed about one week after the first crawlers are seen. If populations are heavy, a second application two weeks after the first should be used. These applications aimed at the crawlers have little effect on the adult scales. Because San Jose Scale occur on all parts of the tree, spray coverage as well as are very critical to effective control. Although there is a second generation later in the summer, crawlers emerge over an extended period of time making insecticidal control of this generation impractical.
For more information on reduced insecticide apple management programs, see EntFact 201, Controlling Apple Pests..
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
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