Black cutworm

What is black cutworm?

The black cutworm is a moth caterpillar found in many parts of the world. It cannot survive winter where the ground freezes, so in the North moths arrive each spring, carried on winds from the South, and then raise two to three generations. Cornell calls it especially damaging on golf greens and tees, and UMass says it is the most common cutworm in New England.

In turf, the caterpillars make burrows or move into aeration holes on greens and come out at night to chew grass around the opening. That leaves small dead spots, brown crescents and pits that can look like ball marks or disease. NC State notes it is usually a problem on closely mowed golf turf and rarely on home lawns, where Kentucky bluegrass is a less favored host.

In gardens, older caterpillars are the classic 'cutworm': they hide in the soil by day and cut young plants at the soil line at night, sometimes pulling them partly underground. UF/IFAS says more than 80 percent of a larva's feeding happens in its last stage, so damage seems to appear suddenly.

Signs and damage

• On golf greens and tees: small circular dead spots, finger-sized brown crescents, or spots that look like ball marks, often around aeration holes (NC State, UMass).
• Pencil-sized burrows in the turf with grass scalped around the opening.
• In gardens: young transplants and seedlings cut off at the soil line overnight, sometimes pulled partly underground.
• Dark gray to nearly black caterpillars with coarse, granular skin hiding in the soil near damaged plants during the day.

Black cutworm identification: what to look for

• Larva: Light gray, gray-brown or nearly black, with many coarse dark granules on the skin and a brownish, spotted head (UF/IFAS); Cornell and NC State note a pale stripe on the back. Usually six or seven stages, reaching about 50 mm (2 inches).
• Adult: Moth with a 40 to 55 mm wingspan. Forewings dark brown, especially near the base, with a lighter band toward the edge and a small black dash; NC State notes a pair of black triangular marks. Hindwings whitish to gray.
• Eggs: Tiny, ribbed, white turning brown. NC State says they are laid singly on grass blade tips; UF/IFAS says moths prefer low broadleaf plants. A female may lay 1,200 to 1,900. They hatch in about 3 to 10 days.
• Damage: Night feeding around burrows on greens and tees; seedlings cut at the soil line in gardens.
• Timing: Moths arrive in spring in northern states; NC State notes activity is usually highest in spring and fall. Larvae feed 20 to 45 days, then pupate in the soil for about two weeks.

Life cycle

Moths migrate north in spring and lay eggs on grass blade tips or low-growing plants. Eggs hatch in 3 to 10 days. Young caterpillars feed on leaves; from about the fourth stage they hide in the soil or a burrow by day and come out at night to feed, cutting plants at the soil line. After 20 to 45 days they pupate about 1 to 5 inches (3 to 12 cm) underground for about 12 to 20 days. The full cycle takes 35 to 60 days, giving 2 to 4 generations a year in most of the U.S. and up to 6 in the Southeast. Pupae cannot survive winter where the soil freezes (UF/IFAS, NC State, Cornell).

When to look: On golf courses, start soap-flush checks one to two weeks after the first spring moth catches in traps (Cornell). In gardens, protect transplants from planting time through early summer.

Black cutworm look-alikes

A few things get mixed up with it:

• Other cutworms (Nephelodes minians, Feltia subterranea and others): Bronzed, granulate and variegated cutworms look similar and are hard to tell apart; they are more likely than black cutworm to show up in home lawns (NC State).
• Sod webworms (Several species (Parapediasia teterrella, Pediasia trisecta and others)): Smaller, spotted, hairy caterpillars that live in silk-lined tunnels with green frass, mostly in lawns.
• Fall armyworm (Spodoptera frugiperda): Has a pale upside-down Y on the head, skin that is granular but not rough, and feeds in groups that move across turf.

How to control black cutworm

Cultural control

• On greens and tees, collect clippings (eggs sit on blade tips) and dump them at least 100 feet from susceptible turf (Cornell, NC State).
• Use a buffer of Kentucky bluegrass around greens; black cutworms avoid it (Cornell, NC State).
• Endophytic perennial ryegrass and tall fescue are less suitable hosts (Cornell).
• In gardens, put a collar around each transplant stem, such as a can or waxed paper cup with both ends removed or a band of foil pushed into the soil, and add row covers since moths can get past collars (UF/IFAS).
• UF/IFAS notes cutworms often feed on weeds first; destroying weeds right before planting can push larvae onto crops, so time weed removal with that in mind.

Biological control

• Insect-parasitic nematodes (Steinernema carpocapsae) work best on small cutworms (Cornell, NC State).
• Cornell lists spinosad and Bt products as biological options most effective on small larvae; UF/IFAS notes Bt is not usually recommended for cutworm control.
• Many parasitic wasps and flies attack black cutworm, and ground beetles prey on it; UF/IFAS reports parasitism as high as 69 percent in Missouri. Flowering weeds help feed these parasites.

Chemical control

On turf, treat late in the day or evening so caterpillars contact the product at night, mow beforehand, use liquids, and hold off mowing and irrigation for 12 to 24 hours afterward (NC State, Cornell). NC State uses a rough threshold of 2 to 6 larvae per square yard, and Cornell says 3 to 4 large larvae on a green may justify control. NC State also suggests treating a 20 to 30 foot buffer around greens and tees to slow migration from outlying areas. NC State's cutworm table names active ingredients such as chlorantraniliprole, spinosad, indoxacarb, carbaryl, trichlorfon, bifenthrin and lambda-cyhalothrin. Use only products labeled for this use; the label is the law.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Monitor golf courses with black light or pheromone traps in spring, and start checking for larvae one to two weeks after the first moth catches (Cornell).
• Remove clippings from greens during egg laying.
• Collar garden transplants at planting time.

When to call a pro

Golf courses should work with a licensed pesticide applicator (see our pesticide applicator license guide) when soap flushes on greens show cutworms above the threshold.

Related guides: Weed identification guide · All pests and diseases

Questions about black cutworm

Similar pests and diseases