Landscape - Scale Insects: San Jose Scale

This is the tenth in a series on scale insects in the landscape. This post is on the San Jose Scale. Information is from the University of Maryland.

San Jose Scale (Quadraspidiotus perniciosus), Family Diaspididae

Plants Damaged: This armored scale can be found on apples, crabapples, and ornamental and edible plums, peaches and pears. It will also feed on cherry laurel, cotoneaster, pyracantha, rose, and other plants in the rose family.

Damage Symptoms: It feeds on the twigs and small branches and weakens the plant.
Yellowing of foliage and dieback of branches

Life Cycle: San Jose scale has three generations per year. The 3rd generation crawlers are still active in October. On apples the crawlers will move out onto the fruit in the first crawler emergence in May and during the second crawler emergence in July. The 3rd generation crawlers tend to be found on the twigs and branches and less on the fruit. On apples you will see round red circles on the fruit.

Monitoring: The female covers are light brown and round with a raised center. Examine
branches and twigs for the presence of overwintering female covers. Use a hand lens to examine foliage for presence of bright yellow crawlers which emerge in May and June.

Control: Target the crawler stage for the best control. Apply Distance and 1 % horticultural oil.


Information from "Scales Commonly Encountered in Maryland Landscapes and Nurseries" by Stanton Gill, Extension Specialist in IPM for Nurseries and Greenhouses,and Suzanne Klick and Shannon Wadkins, Technicians, Central Maryland Research and Education Center University of Maryland Cooperative Extension.