Cherry slug (pear slug, cherry sawfly, pear sawfly)

Cherry slug sawfly larvae are slimy, olive-green, wrinkled creatures that feed on cherry and pear leaf undersides, skeletonizing the tissue and leaving a lacy, brown appearance. You will see the damage in early to mid-summer as the leaf surface browns while veins remain. The larvae look like small slugs because of their shiny coating. Feed occurs on Prunus cerasifera in Western Washington landscaping, and damage can intensify if populations go unchecked but rarely kills trees.

Spray affected leaves with water to physically remove the slug-like larvae; they cannot withstand direct water impact. Conserve parasitoid wasps and other natural enemies by avoiding broad-spectrum insecticides. Insecticidal soap targets young larvae effectively when applied early in the season as soon as skeletonization appears. Most years populations remain light enough that no treatment is necessary; leaf drop later in the season causes minimal long-term impact to tree vigor.