How to Manage Pests
UC Pest Management Guidelines
(Reviewed 7/17, updated 7/17)
In this Guideline:
Monitor during the dormant period to determine the need for a spring sprays to manage populations of walnut scale, frosted scale, European fruit lecanium scale, San Jose scale, Italian pear scale, and European red mite.
How to monitor
These scale treatment thresholds are based on direct damage from scale; they do not reflect thresholds if Botryosphaeria is a concern in your orchard.
Natural enemies often cannot be relied on to keep walnut scale from causing damage. If scales are present but a high degree of parasitization is observed, insecticide applications probably are not needed.
If you find 5 or more nymphs per foot of last year's wood throughout the orchard and less than 90% parasitized nymphs, an insecticide application is warranted.
Same as frosted scale.
If you find 5 or more black caps per foot of last year's wood and less than 90% parasitism, an insecticide application is warranted.
No damage threshold levels are available to determine if an insecticide application is needed. The key to managing Italian pear scales is to control the lichens. Regular blight treatments in spring will provide control of moss and lichens.
No damage threshold levels are available to determine if an insecticide application is needed. Avoid spraying low to moderate levels of European red mites because they can be important in maintaining predators of other mites.
UC IPM Pest Management Guidelines:
J. A. Grant, UC Cooperative Extension, San Joaquin County (crop team leader)