Cutworms
Cutworms are the caterpillars of several night-flying moths. The black cutworm (Agrotis ipsilon) and the variegated cutworm (Peridroma saucia) are two of the most damaging garden species. By day they hide in the soil, curled in a C; at night they come up and chew through the stems of young plants at or just below the soil line. The damage is worst in spring, on small transplants and seedlings. A collar pushed into the soil around each stem is the standard garden fix, and hand-picking by torchlight at night is very effective.
A black cutworm curled in the soil next to a tomato transplant cut at the soil line. Photo: pending.
Identification
Full-grown cutworms are 1–2 inches (2.5–5 cm) long, plump, smooth-skinned and usually dull: grey, brown, tan, pinkish or nearly black, sometimes spotted or striped. Disturbed, they curl into a tight C. That habit, and finding them in the soil at the base of a cut plant, is the practical identification. The black cutworm is greasy grey to nearly black, with coarse dark granules over the body. The variegated cutworm is pale grey to dark brown with red and yellow markings, and it climbs: it feeds on leaves, buds and fruit as well as stems.
The adults are stout brown or greyish moths about 1 inch (2.5 cm) long. Minnesota Extension gives a wingspan of up to 1½ inches (4 cm) and UMass 1–2 inches; the black cutworm moth spans 1.6–2.2 inches (40–55 mm). The front wings are darker than the hind wings. They fly at night and come to lights. Cutworms are easy to confuse with white grubs, which are C-shaped too but creamy white with a brown head and three pairs of legs, and with armyworms, which do similar damage but feed in groups rather than alone.
Easily confused with
- ArmywormsAlso a pestEggs are laid in masses and the caterpillars feed as a group, marching across plants when food runs short. Cutworms feed alone, and both curl up when disturbed.
- White grubsAlso a pestAlso curled into a C, but creamy white with a brown head and three pairs of legs near the head; they are beetle larvae feeding on roots, not caterpillars cutting stems.
- Sod webwormsAlso a pestSlender and smaller, up to about ¾–1 inch, brownish to greyish with black spots, hiding by day in silk-lined tunnels at the soil surface. Lawn cutworms are fat and up to 2 inches.
Damage symptoms
Cutworm damage is most severe early in the season, while plants are small. A larva that has grown past about half an inch stops nibbling leaves and starts cutting stems. It works at night, so the damage appears overnight. Climbing species such as the variegated cutworm also chew buds, leaves and fruit, and the fruit touching the ground suffers most.
- Seedlings or transplants cut through at or just below the soil line, the top lying beside the stump
- Several plants in a row felled in one night
- Irregular holes in low leaves, and in fruit resting on the soil
- A grey or brown caterpillar curled in a C in the soil or under clods near the damage
- In lawns: small dead or sunken spots, and grass clipped around aeration holes
Lifecycle & degree days
The black cutworm cannot survive the winter much north of Tennessee. Each spring, moths ride south winds northward, covering around 1,000 km (620 miles) in two to four days. Some other species, including the dingy, bronzed and glassy cutworms, overwinter locally as eggs or larvae in weedy or grassy ground. The larvae shelter in weeds and plant debris, so a bed that was weedy before planting is the classic trouble spot. There can be three generations a year in Minnesota and two to four across most of the US; UMass notes up to six in some regions.
- Generations / yr
- 1–2 in Canada, 2–4 in the US (up to 6 in some regions); up to 3 in Minnesota
- Eggs per female
- 1,200–1,900 (black cutworm)
- Larval period
- 20–40 days, usually 6–7 instars (5–9 recorded)
- Overwinters
- Black cutworm migrates north each spring; others as eggs or larvae in weeds
- Degree days (black cutworm)
- Base 50 °F: hatch at 90, cutting stage at 431, pupation at 641
Host crops
Cutworms are generalists. Minnesota Extension lists asparagus, beans, cabbage, carrots, celery, corn, lettuce, peas, peppers, potatoes and tomatoes, and the black cutworm feeds on nearly every vegetable and on weeds such as lambsquarters and pigweed. What matters more than the crop is its size: a young transplant with a thin stem is the target.
Monitoring & action thresholds
UC IPM's tomato guidance is to treat only when cutworms are actually found, because damage is often patchy. For lawns, UC IPM gives 5 larvae per square yard in a soap flush. On vegetable farms, Minnesota starts its black cutworm degree-day count when a pheromone trap catches 8 or more moths over two nights. That is a farm scouting tool, not a garden threshold.
Walk the beds in the late afternoon and evening, or after dark with a torch, when cutworms are active, and check again in the morning when damage is fresh. Where a plant has been cut, run your hand over the soil and turn over clods within a foot (30 cm) of the stump; a disturbed cutworm curls into a C. Finding cut plants and no larva is common. In lawns, a soap flush brings them up: UC IPM mixes 3–4 tablespoons of dish soap in 2 gallons of water, pours it over a square yard and counts for 10 minutes.
Biological control
Cutworms have plenty of natural enemies. Ground beetles appear to eat large numbers of the larvae. Parasitic wasps and flies attack them, and there are reports from Missouri of 69% of black cutworm larvae parasitised. Birds pick them out of lawns. The insect-killing nematode Steinernema carpocapsae is the one you can buy that suits them. It ambushes insects moving over the soil surface. Wild insect-killing nematodes in the soil also infect cutworms, but their numbers normally need topping up to give high kill rates. (A different, unrelated wild nematode, Hexamermis arvalis, parasitises up to 60% of black cutworm larvae in the central US.) Bt is weaker here than against leaf-feeding caterpillars. It only works on small larvae that eat treated leaves, and UF/IFAS says it is not usually recommended for cutworms.
Cultural controls
Physical protection is the standard garden fix, because it stops the cutworm reaching the stem. UF/IFAS adds that collars alone may do little where moths keep laying eggs nearby, and that row covers used as well should work better. Clear weeds well ahead of planting: they are the cover and food young larvae depend on, but UF/IFAS warns that killing weeds just as the crop goes in pushes the larvae onto the crop.
- Put a collar round each transplant: a strip of cardboard or paper, a band of foil or a bottomless tin can, pushed a few inches into the soil and standing several inches above it
- Clear weeds and till or dig the bed at least two weeks before planting
- Search at night with a torch and pick the caterpillars off
- Dig round any cut plant in the morning to find the one that did it
- Set out sturdy transplants rather than sowing direct where cutworms have been a problem
- Clear crop debris after harvest, where larvae and pupae shelter
Chemical, last resort
Sources
UC IPM Home and Landscape: Cutworms (web page, accessed 2026)
UC IPM Pest Management Guidelines: Tomato — Cutworms (Natwick et al., 12/13)
UC IPM Pest Management Guidelines: Turfgrass — Cutworms and Armyworms (Sutherland et al., 09/09)
UC IPM Pest Notes 7476, Lawn Insects (Sutherland, Dreistadt & Harivandi, 09/2014)
University of Minnesota Extension, Cutworms (Schuh, Hahn & Wold-Burkness, reviewed 2023)
UF/IFAS EDIS EENY-395, Black Cutworm, Agrotis ipsilon (Capinera)
UConn Home & Garden Education Center, Cutworms (2016)
UMass Extension Turf Program, Cutworms (Vittum, rev. 05/2011)
DiPel DF label, EPA Reg. 73049-39 (2022)
PNW544, Using Entomopathogenic Nematodes for Crop Insect Pest Control (rev. 2012)
University of Kentucky ENT-10, Controlling White Grubs in Turfgrass
University of Minnesota Extension, Sod webworms
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Cutworms by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.