Cutworms

Cutworms are not really worms. They are caterpillars and they will damage or kill pretty much anything in your garden.
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Cutworm caterpillars are the larval stage of several different types of nocturnal moths. Most of them are members of the Noctuid family, but not all.

Large yellow underwing cutworm larva (Neil Phillips) CC BY 2.0

Damage caused by cutworms

Cutworms get their name because of the way they chew through young plant stems, cutting them off just above or just below soil level. Some species burrow into fruit that is lying on the ground or growing low on the host plant, where they can feed in relative safety. Some species of cutworms are more aggressive, climbing up the nearest plant to feed on leaves, buds, and young shoots.

Cutworms will feed on whatever is nearby, but they show a strong preference for celery, tomatoes, peas, peppers, asparagus, beans, berries, melons and other cucurbits, cabbage, beets, rutabaga, lettuce, basil, potatoes, and grapes. Some cutworms will also feed on your lawn. [Maybe I should have just listed what they don't eat...]

Symptoms of cutworm feeding can take many forms. In some cases, it will look a lot like damping-off disease, as seedlings are found in the morning, bent over and dying. On lettuce, holes in leaves and along the edges of leaves may look like slug or snail feeding. On other plants, the young caterpillars will skeletonize the underside of leaves before eating the entire leaf. The only way to be sure is to gently work the soil around damaged plants, looking for the little beasties.

Variegated cutworm moth (Fvlamoen) CC BY-SA 3.0

Variegated cutworm larva (Lacy L. Hyche, Auburn University, U.S. Forest Service) CC BY 3.0 us

Black cutworm moth (Caroline Harding) CC BY 3.0 au

Black cutworm caterpillar (Rasbak) CC BY-SA 3.0

Cutworm description

Adult cutworm moths are usually mottled gray or brown and 1" long. Eggs are laid singly or in clusters in the soil or leaf litter, where they will be close to a food supply. The caterpillars can be 1 to 2 inches long and are usually dull brown or gray. Their skin is smooth and they tend to blend in with the local soil. Many varieties of cutworm curl up into a C-shape when frightened. Once they have eaten enough, the caterpillars pupate in the soil in a reddish brown casing that may be found when tilling the soil. There are three types of cutworm that are commonly found in San Jose, California: black, variegated, and granulate.

Granulate cutworm moth and larva (UG Archive, University of Georgia, bugwood.org) CC BY 3.0 us

Cutworm management​

Cutworm damage can be controlled using these methods:

• Rotate crops.
• Remove weeds that may provide habitat.
• Dispose of infested plants that may contain eggs.
• Use a flashlight to inspect plants at night and remove cutworms by hand.
• Plant seedlings with cardboard collars (toilet paper and paper towel tubes work well).
• Larger plants can be protected with sticky tape.
• Using wood ash to create a protective ring around vulnerable plants may help.