Cutworms in the Home Vegetable Garden
Cutworms can be somewhat difficult to identify because, although they’re true caterpillars, cutworms are about a quarter of the size of other caterpillars and can be found feeding in the soil as opposed to directly on foliage. While most caterpillars are leaf-eaters, cutworms exclusively feed on roots and portions of stem just above the soil.
The name “cutworm” does not refer to a single individual species of caterpillar but actually describes the damage done to plants by a wide variety of caterpillars that “cut down” their host at the stem rather than feed on foliage.
Like any caterpillar, the cutworm can be very destructive because they are young, hungry, and maturing larvae that must feed voraciously before transitioning into an adult brown moth.
Though cutworms are solitary pests like slugs or grasshoppers, just one cutworm is enough to decimate an entire host plant overnight.
Facts About Cutworm Garden Pests
- Cutworm Distribution: Cutworm brown moths are naturalized on 6 of 7 continents
- Cutworm Host Plants: Transplants and seedlings of just about anything especially potato, cabbage, pea, mint
- Cutworm Lifespan: 4-8 weeks as a larval caterpillar
- Cutworm Eggs Laid per Lifetime: ~1,000
- Cutworm Removal: Bacillus thuringiensis var. kurstaki (Bt), tilling, birds
- Cutworm Predators: Birds, beetles, spiders, nematodes, lacewings, parasitic wasps
- Most Common Cutworm in North America: Variegated Cutworm Peridroma saucia
What Do Cutworms Look Like?
Despite the name, cutworms are actually larval caterpillars of the brown moth and share no similarities to worms other than name. Cutworms are much smaller in size when compared to other caterpillars such as the tomato hornworm and are often mistaken for grubs when found coiling and retracting in the soil.
The most extensive species of cutworm in North America is the variegated cutworm which only reaches 1-2” long and has a brown mottled, patternless exterior with a slight row of pale spots down the center of its spine.
Cutworms can be very difficult to identify because they are merely a quarter of the size of other caterpillars and can easily be mistaken for a maggot or worm when found in soil.
Cutworm Damage to Garden Vegetables
The name “cutworm” does not refer to a single individual species of caterpillar, but actually describes the damage done to plants by a wide variety of caterpillars that “cut down” their host.
Unlike larger, more familiar caterpillars that feed on leaves, pods, and seeds, cutworms are smaller soil-based caterpillars that exclusively feed on young seedlings, stems, and roots. This type of aggressive feeding at the base of a host plant eventually causes it to fall over as if it has been “cut down” at the stem or roots.
Some cutworms are known as climbing cutworms because they have adapted to scale up the host plant and feed on foliage traditionally like much larger caterpillars.
What Do Cutworms Eat in the Garden?
Soil-based cutworms feed on just about any seedling in the garden and have been shown to have the widest and most extensive diet of any caterpillar in North America. As mentioned, cutworms generally feed on the roots and stems of plants without regard as to whether it's a fruit, vegetable, or herb.
While nearly anything in the garden is at risk for a cutworm damage, crops such as tomato, pea, potato, cabbage, and mint have been found to be slightly more susceptible than others.
Although most cutworms in North America are solitary and do not swarm, there is a swarming variety referred to as “armyworm” which is known to infest fields, grasses, legumes, and fruiting trees occasionally detected in the southern and eastern states.
Cutworm eggs laid by the fully-matured brown moth can be easily spotted on a blade of grass, stem, or a leaf, not necessarily on the protective underside like most insects. Brown moths will lay about 60 eggs at a time in a tightly packed, uniformed, and efficient pattern.
Depending on the exact species of cutworm, eggs can be white, black, translucent, or pale yellow. Eggs hatch in 4-10 days depending on climate before spawning the aggressively hungry caterpillar larvae. Variegated cutworm eggs can be easier to spot than others because they are not kept hidden on the underside of leaves and have distinct ridges and a barrel-shaped appearance.
Adult moths can lay up to 1,000 eggs in their brief 6-8 weeks of reproductive maturity.
How To Get Rid of Cutworms
Cutworms are merely soft-bodied caterpillars and can be eradicated from the garden as easily as any other caterpillar.
One of the most popular remedies to removing caterpillars of any kind is to lightly spray the affected areas of your crops with store-bought Bacillus thuringiensis, or simply known as Bt. The bacteria is non-toxic to humans and animals but very effective when consumed by caterpillars. There are several types of Bt for different insects but, if eradicating cutworms and hornworms, be sure to only use Bacillus thuringiensis var. kurstaki.
Keeping an active and bustling bird feeder nearby will invite countless birds into your garden that will no doubetdly root through your soil for grubs, slugs, and cutworms.