How to Manage Pests

UC Pest Management Guidelines

Walnut

Italian Pear Scale

Scientific Name: Epidiaspis leperii

(Reviewed 12/07, updated 4/09)

In this Guideline:


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, but with a brown peak slightly off-center. 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.

DAMAGE

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

MANAGEMENT

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 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 material such as Bordeaux mixture or hydrated lime to the dormant spray to kill them. For information on making a Bordeaux mixture, see UC IPM Pest Note: Bordeaux Mixture, ANR Publication 7481.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

Insects and Mites

  • C. Pickel, UC IPM Program/UC Cooperative Extension, Sutter/Yuba counties
  • J. A. Grant, UC Cooperative Extension, San Joaquin County
  • W. J. Bentley, UC IPM Program/Kearney Agricultural Center, Parlier
  • J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
  • W. W. Coates, UC Cooperative Extension, San Benito County
  • R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
  • W. H. Olson, UC Cooperative Extension, Butte County
  • L. C. Hendricks, UC Cooperative Extension, Merced County
  • G. S. Sibbett, UC Cooperative Extension, Tulare County

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