Combating Rose Slugs on Knock Out Roses: Effective Treatments and Timing

Identifying Rose Slug Damage

Rose slugs (actually sawfly larvae) feed on the undersides of leaves, scraping away tissue and leaving a characteristic lacy, skeletonized appearance. They are small, greenish, and slug-like, often overlooked until damage is extensive.

Why Not to Prune Infested Bushes

Even damaged leaves contribute energy through photosynthesis. Removing them weakens the plant further. Keep the foliage and treat the pest instead.

Recommended Controls

• Systemic insecticides containing cyfluthrin (e.g., Bayer Advanced) or acephate (Orthene) move into leaf tissue, killing larvae when they feed.
• Contact sprays like Sevin are less effective because larvae feed under leaves where spray coverage is poor.

Prevention for Next Year

Rose slugs overwinter as pupae in soil around the base. In early May, apply a systemic insecticide to the plant and drench the surrounding soil to intercept the first generation.