Cutworms: Damaging Pests in Gardens & Crops

Cutworms are the larval stage of any number of moth species – more than 200, at least. As caterpillars, they do a great deal of damage to yards, plants, and crops. Cutworms do most of their work at night, gnawing away at the bases of plant stems and in some cases, the root systems. Once they become adults, they’re harmless, feeding mainly on nectar. As a group, they’re known as owlet, or miller, moths.

The life cycles are the same among all miller moth species. Depending on the climate, however, they may have one or more caterpillar emergence seasons annually. This allows for plenty of time to eat away the intended targets in the cutworm stage.

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Common cutworm varieties include:
-army worm
-black cutworm
-bronzed cutworm
-dingy cutworm
-glassy cutworm
-granulate cutworm
-sandhill cutworm

Depending on the species, they attack plants in varying ways:
-climbing to consume leaves, tender shoots and fruit.
-surface gnawing that fells a plant at or near the base
-underground activity that includes feeding on and destroying the root system.
-wide coverage, especially in the case of army cutworms that decimate the upper portion of plants in a wave.

Growth stages are similar among all cutworms, although variances may occur. Generally, the female lays eggs in the fall, which hatch and hide under debris during the winter. They continue to grow, emerging as good-sized larvae when the weather warms. They move swiftly and can create a great deal of damage overnight in smaller areas. Many will not reach the pupae stage until almost mid-summer, which explains the great amount of destruction. Cutworms are typically single generation in cooler regions and may be in greater abundance following a dry season. In southern states, two-four generations may be occur.

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Because cutworms generally feed at night, identification can be difficult until early indications of damage are present. Digging in the general vicinity of plants may produce the worms. They’ll be as small as a half-inch in length up to two inches.

For the home gardener, physical barriers are recommended for above ground species. These include any container that is open on both ends and buried around the plants. Soaking the ground with an insecticidal soap and water solution can also cause the cutworms to rise to the surface. Pesticides for cutworm control include Diazinon and Sevin. These may not be effective on subterranean cutworms. It is also important to identify the specific type of cutworm before taking chemical measures.

Improving the quality of soil over the winter or across two seasons may also reduce cutworm populations. Heavy tilling will bring buried worms to the surface that can be picked off by birds. Removing mulch and all plant materials during winter exposes the soil to sunlight, making it less habitable.

Cutworms of any type are serious pests that require vigilance and early prevention.

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