Brown Worms (Caterpillars) on Roses: Bt, Sprays, and Soil Health

Identification

Brown worms under leaves = caterpillars (likely sawfly larvae/rose slugs). They skeletonize leaves.

Stop high-N fertilizers—they make soft, tasty growth.
Switch to organic rose fertilizer.
Sprays: Bt (Bacillus thuringiensis) stops feeding; organic liquid fertilizer or compost tea on foliage; red sticky traps.
Soil health: compost, rock dust, mulch to raise plant Brix (sugar/mineral level), making leaves less palatable.

Healthy, mineralized roses resist pests naturally.

Roses: Old Rose Bush Buds Turning Brown: Rose Midge or Rootstock Takeover?; Best Roses for Shady North-Facing Gardens in Ontario: Rugosas and Hybrid Musks; Controlling Caterpillars on Knock Out Roses with Simple Soap Sprays; Brown, Crispy Rose Buds? Rose Midge Infestation and Systemic Insecticide Limitations; Cool, Wet Springs Cause Botrytis Blight on Hybrid Tea Rose Buds; Red Rose Buds Turning Brown Before Opening – Midge or Botrytis?; Controlling Caterpillars on Miniature Roses; Brown Roses Exist: The Uncommon World of Russet Blooms; Green Worms with Orange Heads on Potted Roses: Sawfly Larvae (Rose Slugs) and Organic Control; Dealing with Worms in Bird of Paradise Potting Soil

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