Cutworms

Beneficial nematodes (Steinernema carpocapsae) applied to moist soil target cutworm larvae underground — apply at dusk when soil is above 55F (13C) and keep moist for 2 weeks. This is the most effective biological control for soil-dwelling larvae. Ground beetles are the most important surface predator of cutworm eggs and young larvae — permanent undisturbed mulch paths support ground beetle populations year-round. Parasitic wasps (Apanteles spp.) parasitize larger larvae. Robins and starlings actively dig cutworm larvae from soil after tilling — encourage insectivorous birds with habitat near the garden.

Cutworms cut seedlings at the soil line overnight — you find healthy plants toppled with a clean cut at the base and no insect visible. They feed at night and hide in soil during the day. The most effective prevention is a physical collar around each seedling — a toilet paper roll, plastic cup with the bottom removed, or tin can pushed 1 inch into soil creates a barrier cutworms cannot cross. Install collars at transplanting, not after damage appears. Till or cultivate beds 2 weeks before planting to expose pupae and eggs to birds and desiccation.

Cutworm moths lay eggs on w planting areas 2 weeks before transplanting and till to expose larvae. Remove crop debris after harvest. Delay transplanting slightly after clearing — birds and beneficial insects will work the exposed soil. Diatomaceous earth applied as a band at the soil surface around plant stems damages cutworms crossing at night. Cornmeal placed near plants is consumed by cutworms but they cannot digest it — an old folk remedy with some documented effectiveness.

Cardboard or plastic collars pushed 1 inch into soil around each seedling are the most reliable mechanical control — they physically stop cutworms from reaching stems. Check by digging in soil near cut plants during the day — cutworms curl up 1-2 inches below the surface near their feeding site. Hand-pick and destroy. Tilling and cultivating before planting exposes larvae to birds and desiccation — do it repeatedly in the 2 weeks before transplanting for maximum effect.

Bt kurstaki applied to soil surface and lower plant stems at dusk kills young cutworm larvae that feed on treated surfaces — most effective on larvae under 1 inch. Spinosad as a soil drench reaches cutworms below the surface. Diatomaceous earth applied as a dry band at soil level damages cutworms crossing at night — must be reapplied after rain. Neem oil soil drench disrupts larval development. Apply all treatments at dusk when cutworms are beginning to emerge and feed.