WSU Extension

Hortsense

Walnut
 
Disease
Anthracnose (Blotch) 
Blackline 
Blight 
Thousand cankers disease 
Insect
European fruit lecanium 
Walnut aphid 
Walnut blister mite 
Walnut husk fly 
Walnut twig beetle 



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Caption: Lecanium scales
Photo by: R.S. Byther
  
Walnut : European fruit lecanium
(revision date: 3/10/2017)


Biology
The European fruit lecanium is a shiny brown scale insect found on twigs. Adults are 1/8"-1/4" in diameter and roughly turtle-shaped. They may have light markings or appear somewhat waxy. Crawlers (immature scales) are flatter and may be found on leaves. Scales produce large amounts of honeydew, a sweet, sticky material which may attract ants or become covered with a growth of dark sooty mold. Heavily infested branches may be wilted, yellowish, or show other signs of stress. New growth may be stunted or lacking. This lecanium scale closely resembles frosted scale, but does not produce the waxy coating found on frosted scale in the spring. Lecanium scales are common pests in the landscape, infesting many plants including maple, rhododendron, and fruit trees.
Management Options


Non-Chemical Management
  • Natural enemies such as ladybird beetles, green lacewings, and parasitic wasps help control scale populations. Avoid use of broad-spectrum insecticides which kill these and other beneficial insects.
  • Control honeydew-feeding ants which may protect scales from predators.
  • Hand-wipe to help control minor infestations.
  • Prune and destroy heavily infested branches, when practical.
Select non-chemical management options as your first choice!

Chemical Management

Apply oil during delayed-dormant period (when buds start to swell) to control crawlers. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bayer Advanced Natria Neem Oil RTU/Roses, Flowers, Fruits & Vegetables [Organic]
    Active ingredient: clarified hydrophobic extract of neem oil  |  EPA reg no: 70051-13-72155
  • Bug Buster-O [Organic]
    Active ingredient: pyrethrins  |  EPA reg no: 1021-1771-54705
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap with Seaweed Extract II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-59
  • This list may not include all products registered for this use.
Images

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Caption: Lecanium scales
Photo by: R.S. Byther