The Life Cycle of a Cutworm

Cutworms eat through corn, peppers, beans and other crops.

Cutworm is the term for the larval stage of some moths, a name earned by the way they cut down the plants on which they feed. The highly destructive cutworms readily eat through crops and vegetation, such as beans, peppers, corn and tomato plants. A cutworm's life cycle from an egg to an adult moth can take as few as 30 days in midsummer or longer if the larvae are forced to hide over the winter.

Types and Appearance

Cutworms have many different species and types, categorized by the way they feed. Surface cutworms hack the plants down near the surface of the soil. Climbing cutworms shimmy up the plant stems to eat the buds, fruit and leaves. Subterranean cutworms live in the dirt, feeding on the plant roots. Army cutworms work in large groups, eating off the tops of plants before they moving onward to their next conquest. Cutworm colors range from black to brown, usually with a smooth outer skin. Some feature yellow spots while others are striped, variegated or have a glassy appearance.

Eggs

Late summer is breeding time for moths. A single adult female moth can lay hundreds of eggs during one season. Some lay eggs singly, while others lay them in clusters or patches. They try to pick out areas that are covered with lots of grass or weeds and lay their eggs near or in the dirt. The white, ribbed eggs are round and tiny, about half the size of a pinhead. If the weather is still warm enough, five days is all it takes for the eggs to hatch.

Larvae

Once they hatch in the weedy or grassy patch, larvae, or caterpillars, begin to feed on the plant life immediately. They will continue to feed until the cold winter hits and they are forced to retreat to shelter. Most cutworms spend their winters hiding out, although a small number of species have already reached the pupae or moth stages and spend the cold season hibernating. Those that remain in the larval stage find hideouts in soil, grass or in piles of trash or bark. The moment the weather warms up for spring, their feeding frenzy begins. The frenzy lasts through June for many species, when the larvae move on to the pupal stage. Larvae stop feeding once they hit about one-half inch in length, one-third of their full grown length of about 1.5 inches.

Pupae

The full grown larvae move on to the pupal stage. To enter this resting stage, the larvae drop from the plants on which they were feeding and burrow into the soil. As they burrow through the soil, the larva creates a small tunnel for itself, about three inches from the top of the soil. There the larva sits in the pupal stage, surrounded by its brown pupal case, for as few as 10 and as many as 25 days until it emerges as a moth. If the tunnel they set up when they entered the dirt happens to cave in or is blocked, the moth cannot get out and instead dies trapped in the soil.

Adults

The moth is the adult stage of cutworms, a time when the previously destructive worm has transformed into a harmless moth. While the adult moths will not eat and destroy plant life as the cutworms do in their larval stage, they will breed at least once per season, creating more of the destructive worms. Adult moths are brown, with dark brown forewings and a pair of white hind wings, both of which fold down into a triangular shape along their backs. Their wingspan ranges from about 1.5 to 2 inches.

References

• University of Rhode Island Cooperative Extension: Cutworms
• University of Minnesota Cooperative Extension: Cutworms in Home Gardens
• Cornell University: Cutworm Life Cycle