Cutworm Life Cycle: A Concise Guide to Understanding these Garden Pests

Cutworms are a common pest and a concern for gardeners and farmers alike. These soft, plump, and hairless caterpillars cause damage to a wide range of plants as they feed on stems and leaves. Their colors and markings can vary, ranging from dingy white to brown, charcoal gray, or even tan source.

There are several species of cutworms, with some native to certain areas and others migrating annually. For instance, some species, like the black and variegated cutworm, migrate into Minnesota each year, while others, like the dingy and glassy cutworms, are native and can overwinter as eggs or larvae in grassy areas source. Understanding the life cycle of cutworms is essential in developing effective pest control strategies and maintaining a healthy garden or crop.

Cutworm Life Cycle

Eggs

Cutworms lay their eggs in various stages depending on the species. Some, like the black cutworm, lay eggs in early spring while others mate and lay eggs from late summer to fall. Eggs are usually laid singly on grass blades or plant stems.

Larvae

The life cycle of a cutworm progresses through multiple stages called instars. Full-grown larvae are 1-2 inches long, hairless caterpillars that vary in color from dingy white to tan, brown or charcoal gray. Cutworm larvae, such as the dingy, bronzed, and glassy cutworms, are native to specific regions and overwinter as eggs or larvae in grassy areas, emerging in the springtime.

Pupa

When a cutworm larva is fully grown, it enters the pupal stage in the soil or inside plant material. During this stage, the larva transforms into an adult moth.

Adult Moths

Cutworm adult moths are night-flying insects with wingspans ranging from 1.5 to 3 inches. Some species, like the variegated and black cutworms, migrate into regions from the south each year, while others are native to their habitats. Adult moths are not harmful to plants, but feed on the nectar of wild and cultivated flowers.

In summary:

• Cutworm life cycle includes eggs, larvae, pupa, and adult moths.
• Eggs are laid on grass blades or plant stems.
• Some species migrate yearly while others are native to specific regions.
• Adult moths feed on flower nectar and are not harmful to plants.

Types of Cutworms

Black Cutworms

Black cutworms, or Agrotis ipsilon, are gray-brown moth larvae that feed on seedlings and transplants. They can be identified by their dark spots and their tendency to curl up into a ball when disturbed¹.

• Size: 1-2 inches long
• Color: gray-brown with dark spots
• Host plants: corn, cabbage, and other vegetables

Variegated Cutworms

Variegated cutworms, or Peridroma saucia, are gray to brown caterpillars with a distinctive white stripe along their sides². They can cause extensive feeding damage on various plants, such as:

• Vegetables
• Field crops
• Turf

Army Cutworms

Army cutworms, also known as armyworms, are notorious for their soil-surface feeding habits that damage root systems of plants. They prefer host plants like:

• Vegetables
• Grasses
• Field crops

These pests belong to the same family as other cutworms, Noctuidae, within the order Lepidoptera³.

Climbing Cutworms

Unlike other cutworms, climbing cutworms prefer to feed on higher parts of plants, like leaves and fruits. They possess a unique camouflage pattern that helps them blend in with their environment. Some of their features include:

• Brown or gray coloration
• No obvious spots
• Striation pattern on their body

Subterranean Cutworms

Subterranean cutworms usually feed on roots and underground stems, causing significant damage to a variety of plants. These root-damaging pests can be found in habitats like:

• Soil surface
• Under vegetative debris

They have a different behavior from the other cutworms, cutting seedling plants at the soil surface and pulling them into their tunnels⁴.

Comparison Table

Feeding Habits and Damage

Plants Affected

Cutworms are generalist feeders with a wide variety of host plants, including:

• Corn
• Cotton
• Sorghum
• Vegetables
• Turf

Signs of Cutworm Infestation

Key indicators of cutworm presence are:

• Chopped off plant stems
• Skips or sections of rows with damaged plants
• Curling up caterpillars when disturbed

Cutworms have three primary feeding habits:

• Surface feeders
• Tunnel dwellers
• Climbing cutworms

Surface feeders chew plant stems from the soil surface, while tunnel dwellers remain underground during the day and damage plants at night. Climbing cutworms are known for climbing up plant stems to feed on foliage.

Preventing Damage

Temperature and Moisture Factors

Cutworms experience difficulty surviving in:

• Dry soil
• High temperatures

More seed treatments and spot treatments are needed during cooler, wetter periods.

Pest Management

Effective cutworm management strategies include:

• Use of insecticides
• Release of natural enemies like nematodes
• Application of soapy water

Keep in mind that pest management practices may also affect other pests, such as leafhoppers and aphids.

By understanding cutworm feeding habits, targeting their preferred host plants and implementing preventive measures, reducing cutworm-related crop damage is achievable.