Cutworm Information
Frequently Asked Questions About Cutworms
Cutworms are one of the most common garden pests in Alberta. These sneaky caterpillars spend the day hidden in the soil and come out at night to feed. Many gardeners first discover them after finding healthy seedlings mysteriously cut off at ground level by morning.
This guide covers identification, prevention, treatment options, and how products like BTK and beneficial nematodes can help protect your plants.
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What are cutworms?
Cutworms are the larvae of several species of moths. These caterpillars typically hide in the soil during the day and emerge at night to feed on plants. Their name comes from their habit of cutting down young seedlings at or just above the soil line.
How do I identify cutworm damage?
The most common sign is a healthy seedling that has been completely severed near the base of the stem overnight. You may also notice wilted plants, missing leaves, or stems that appear chewed through. Cutworms often drag cut plants into their hiding places to feed.
What do cutworms look like?
Most cutworms are smooth-bodied caterpillars that range from grey and brown to green or nearly black. They typically curl into a tight "C" shape when disturbed and can grow up to 5 cm (2 inches) long depending on the species.
When are cutworms most active?
Cutworms are primarily nocturnal. They hide in soil, mulch, plant debris, or cracks during the day and emerge after dark to feed. Damage often appears suddenly overnight.
What plants do cutworms attack?
Cutworms feed on a wide range of vegetables, flowers, herbs, and ornamental plants. Tomatoes, peppers, cabbage, lettuce, beans, corn, sunflowers, and many bedding plants are common targets.
Do cutworms only attack seedlings?
Young seedlings are most vulnerable, but larger cutworms may also chew foliage, stems, flowers, and developing fruit. Some species climb plants and feed above ground.
Will cutworms kill mature plants?
Most established plants can survive some feeding damage, but young transplants and newly emerged seedlings can be completely destroyed by a single cutworm.
How can I find cutworms?
Inspect plants after dark using a flashlight. During the day, gently dig around the base of damaged plants and sift through the top few centimetres of soil. Cutworms are often found curled up nearby.
Does BTK kill cutworms?
BTK (Bacillus thuringiensis var. kurstaki) can kill cutworms if they consume treated foliage. However, because many cutworms spend much of their time hidden in the soil, BTK is generally less effective against cutworms than it is against tent caterpillars, cabbage worms, and loopers.
What is the best treatment for cutworms?
A combination of prevention and biological control usually provides the best results. Stem collars, beneficial nematodes, hand-picking, and removing plant debris can significantly reduce cutworm populations.
Do beneficial nematodes kill cutworms?
Yes. Beneficial nematodes can be highly effective against cutworms by attacking larvae in the soil. They are especially useful in vegetable gardens, raised beds, and greenhouse growing systems.
Can cutworms survive winter?
Many cutworm species overwinter as eggs, larvae, or pupae in the soil. Populations often reappear the following spring when temperatures warm.
Are cutworms harmful to people or pets?
No. Cutworms do not bite, sting, or transmit diseases to people or pets. They are considered a nuisance because of the damage they cause to plants.
How can I prevent cutworm damage?
- Use cardboard or plastic collars around seedlings.
- Remove weeds and plant debris before planting.
- Cultivate soil before planting to expose larvae and pupae.
- Apply beneficial nematodes to susceptible garden areas.
- Monitor young plants regularly during spring and early summer.
Do cutworms eventually become moths?
Yes. Cutworms are the larval stage of various moth species. After feeding, they pupate in the soil and emerge as adult moths that lay the next generation of eggs.
Can a garden recover from cutworm damage?
Absolutely. While cutworms can be frustrating, most infestations are localized and manageable. Replacing damaged seedlings, protecting new transplants, and reducing future populations can quickly restore a healthy garden.