WSU Extension

Hortsense

Hawthorn
 
Disease
Fire blight 
Leaf spot 
Rust 
Scab 
Insect
Apple-and-thorn skeletonizer 
Hawthorn aphid 
Pear slug 
Scale insects 
Spider mites 



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Caption: Apple-and-thorn skeletonizer
Photo by: A.L. Antonelli
  
Hawthorn : Apple-and-thorn skeletonizer
(revision date: 6/23/2015)


Biology
The adult of the apple-and-thorn skeletonizer is a small dark-brown moth. It overwinters as an adult, laying eggs in the spring. The caterpillars are yellow-green in color with black spots and brown heads. They feed on the leaves of several plants including crabapple, apple, pear, cherry, and willow. Characteristic damage includes skeletonized leaves, or leaves that are rolled and tied with webbing. The feeding caterpillars produce large amounts of webbing and small dark frass pellets (excrement).
Management Options


Non-Chemical Management
  • Hand-pick caterpillars.
  • Pinch tied leaves to kill caterpillars inside.
Select non-chemical management options as your first choice!

Chemical Management

Apply if damage is noticed. Several applications may be needed during the season. Bacillus thuringiensis (Bt) will provide control of young feeding caterpillars. Use a spreader-sticker with liquid Bt formulations. Applications made in late spring and early summer for control of aphids and other insect pests often reduce this insect as well. 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.
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • ferti-lome Borer, Bagworm, Tent Caterpillar & Leafminer Spray
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-7401
  • Monterey Garden Insect Spray [Organic]
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-54705
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Caterpillar Killer for Trees, Shrubs & Vegetables Conc II [Organic]
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 70051-106-42697
  • Safer Brand Caterpillar Killer/Trees, Shrubs, & Vegetables Conc
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 42697-23
  • This list may not include all products registered for this use.
Images

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Caption: Apple-and-thorn skeletonizer
Photo by: A.L. Antonelli