WSU Extension

Hortsense

Ornamental Pear
 
Disease
Fire blight 
Pear trellis rust 
Powdery mildew 
Pseudomonas blossom blast and dieback 
Insect
Aphids 
Codling moth 
Pear slug (pear sawfly) 
Pearleaf blister mite 



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Caption: Pear slug and damage
Photo by: R.D. Akre
  
Ornamental Pear : Pear slug (pear sawfly)
(revision date: 2/14/2019)


Biology
The pear sawfly is also known as the pear slug (or 'cherry slug' when on cherry) because of its resemblance to a small, dark slug. These insects are the larval stage of a glossy, black sawfly about 1/5" long. The larvae are covered with a dark green to black slime which gives them the slug-like appearance. The caterpillar-like larvae are yellow immediately after molting until the slime is produced. Larvae are also yellow-orange immediately before pupating. Pear slugs feed on upper leaf surfaces, skeletonizing leaves. Severe infestations can cause defoliation, weaken trees, and affect fruit development on fruiting varieties.
Management Options


Non-Chemical Management
  • Hand removal is effective on small trees.
  • Natural enemies control pear slug populations fairly effectively. Avoid use of broad-spectrum insecticides which can kill beneficial insects.
  • Wash pear slugs from trees with a strong stream of water.
Select non-chemical management options as your first choice!

Chemical Management

Chemical control measures are rarely necessary except for very severe infestations. Apply when larval damage approaches 25% to 30% defoliation. 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.
  • Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 4-472
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • This list may not include all products registered for this use.
Images

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Caption: Pear slug and damage
Photo by: R.D. Akre