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Photo Credit: Tom Weissling

Cutworms feed on the base of plants, then leave their wasteful calling card: a chopped down plant.

The scene is gruesome – even the strongest may turn their gaze: young plants cut down, their bases firmly embedded in the soil, but their dismembered tops strewn about the ground. It’s the work of cutworms…and there are many different species responsible for such damage.

But before we start pointing fingers, let’s clear a few things up: While rebellious in their youth, adult cutworms are innocent of any assault on plants. The adults are nocturnally active moths that fly about, sipping on flower nectar, if they feed at all. That said, they’re not completely innocent. In late summer, these moths emerge from the soil, where they had metamorphosed from a caterpillar into the winged creatures they become. Once they’re out and about, they mate, and the females go off to look for grassy or weedy areas to lay their eggs. These eggs, sometimes hundreds per female, are laid on plant stems or in the soil. And so a new generation of cutworms begins…

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Photo Credit: ©2008 Buglady Consulting

This cutworm larva is in its typical resting position.

Soon after they’re laid, the eggs hatch, and very tiny cutworm larvae go off in search of food. At this point they’re so small (and the plants are so big), that their munching damage goes unnoticed. But they’re out there – feeding and chewing on the base of plants…or on the leaves or perhaps even below the soil surface. (Feeding preference is really related to species. Army cutworms, for example, prefer grasses – especially certain wheat cultivars. In other words, few plants are safe.)

Most feeding stops when fall temperatures are too cold for activity and the caterpillars seek a place to spend the winter, such as under leaf litter, in clumps of grass or even in cells made in the soil. There they wait until spring temperatures warm them up and promote plant growth. They’re very hungry by spring, so seedlings or transplants are at risk.

The pests hide in the soil during the day and come out to feed at night. Most cutworm species chew on the base of plants right at, or just below the soil line, felling the plant. But they only feed on the base, wasting the rest of the plant. This dangerous feasting continues until midsummer, when the fattened caterpillars then crawl into the soil to change into the adult stage.