Agriculture: Walnut Pest Management Guidelines

Italian Pear Scale

Description of the Pest

Italian pear scale overwinters mostly as a mature scale. The cover is circular, about 0.06 inch (1.5 mm) in diameter, and light gray, with a brown, slightly off-center peak. Underneath the covering, the female's body is reddish, purple, or pink, a trait that helps distinguish the Italian pear scale from other armored scales found in walnut orchards. The scale is hidden under moss and lichens and cannot survive without this natural shelter.


This scale does not attack nuts, but feeds directly on the wood of the tree, affecting tree vigor. Light to moderate infestations do not seem to harm trees, but heavy scale aggregations may cause the bark to crack and can reduce tree vigor. Such large numbers are seldom encountered, however, in orchards that are regularly treated for blight.


Look for Italian pear scale during the dormant period when you monitor other scale insects. Pay particular attention to scaffold limbs and branches that are covered with lichens. Scrape the lichens away to look for the gray scale covers and the pink scale bodies beneath. To monitor Italian pear scale with other pests, see DORMANT MONITORING. The key to managing Italian pear scales is to control the lichens. Regular blight treatments in spring will provide control of moss and lichens.

Organically Acceptable Methods

Remove moss and lichen or treat them with Bordeaux mixture when Italian pear scale is a problem. Not all copper compounds are organically acceptable, so be sure to check the label of the product used.

Treatment Decisions

Generally, delayed-dormant sprays applied for other scales control Italian pear scale and blight sprays control the moss and lichens. If moss and lichen are present, add a pesticide such as Bordeaux mixture or hydrated lime to the delayed-dormant spray to kill them. For information on making a Bordeaux mixture, see UC IPM Pest Note: Bordeaux Mixture, ANR Publication 7481.

Common name Amount per acre REI‡ PHI‡
(Example trade name) (hours) (days)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
Oils are not recommended for use during the dormant season on walnut trees and use with caution during the delayed dormant period.
  8-5-100 Label rates See label
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
  COMMENTS: Adding 0.5 gal summer oil emulsion can reduce phytotoxicity. The objective is to apply 4 lb metallic copper and 5 lb of calcium hydroxide in 100 gal water/acre. If using basic copper sulfate, which is 50% copper, apply 8 lb/acre. For hydrated copper sulfate, which is 25% copper, use 16 lb/acre. Not all copper compounds are approved for use in organic production; be sure to check individual products. For information on making Bordeaux mixtures, see UC IPM Pest Note: Bordeaux Mixture, ANR Publication 7481.
Text Updated: 07/17
Treatment Table Updated: 07/17