Plum, Prune (Fresh): Pear slug
categories: Plum, Prune (fresh) Plum, Prune (Fresh) Insects Tree Fruits
revision date: 2022-12-05 12:00
Photo by: R.D. Akre
Biology
The pear sawfly is also known as the pear slug 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 caterpillar-like larvae are covered with a dark green to black slime which gives them the slug-like appearance. The 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. The pear slug prefers cherry (where it is called the cherry slug) and pear, but will also feed on plum.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- 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.
- Hand removal is effective on small trees.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Chemical control measures are rarely necessary except for very severe infestations.
- Apply when larval damage approaches 25% defoliation.
- NOTE: Esfenvalerate is toxic to bees.
- Do not apply products containing esfenvalerate on or near blooming plants.
- To minimize risk to bees, apply in the evening after bees have stopped foraging for the day.
- 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.
Approved Pesticides
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.