Don’t Let Cutworms Take Over Your Garden!

Cutworms may be small, but they can cause a lot of damage. Follow these tips to control an outbreak and keep your seedlings safe from harm.

All gardeners agree: There’s nothing worse than watching seemingly healthy seedlings get decimated out of nowhere. If you suddenly find your garden plants getting snipped off at the base, you may be dealing with a cutworm infestation.

These tiny insects can cause significant damage, but understanding the problem means that you can take steps to get your growing space back under control. Cutworms are found on every continent except Antarctica. They are an extremely prevalent garden pest that can be tricky to control. Here’s how to identify cutworms and keep your garden safe from attack.

What are Cutworms?

There are more than 200 types of insects identified as “cutworms” in the United States. Most are the larvae of night-flying moths in the Noctuidae family. The adult moths lay eggs in grass and weeds, where caterpillars hatch and migrate into the soil.

These small insects curl their bodies around stems to feed on them, slowly cutting off the stem right at the soil surface. They typically live along the soil line and feast on plant stems. Over time, they will completely gnaw off the stem.

Young plants are the most vulnerable because they have the thinnest stems. That’s partly why cutworms tend to cause the most damage in the spring.

Cutworm larvae attack a variety of plants, including kale, cabbage, broccoli, beets, and cauliflower. In the right conditions, they will also go after fruits like strawberries, melons, and tomatoes, and they can attack lawns.

Identifying cutworms can be a challenge since each variety looks somewhat different. Color options range from black to brown, tan, gray, and even pink or green. Many are spotted or striped. Most varieties are smaller than two inches long, and they tend to curl up in a C shape if you poke or pick them up.

You’ll rarely see cutworms on the plants themselves since they hide in the soil during the daytime. Nighttime is when they come out to feed. Cutworms can easily destroy 75% or more of a crop when left untreated.

How to Diagnose Cutworms in the Garden

Identifying whether cutworms are the culprits for your garden’s damage can be a challenge, since the destruction usually happens at night.

One way to tell whether you have cutworms is if an entire row or section of plants are lopped off at the base rather than a few isolated plants. Some will cause damage to foliage, buds, and shoots, and even tunnel into fruit.

When cutworms attack turf grass, they will leave dead brown circles that are easier to identify. One sign of cutworms is when more birds than usual are eating bugs off your lawn.

You may have just one variety of cutworm in your garden, or be dealing with several at once. Regardless, all cutworm infestations require the same treatment.

Treating a Cutworm Infestation

Lose your plants to cutworms once, and you’ll be motivated to eradicate the problem for good. There are many strategies for getting an outbreak under control. Here’s what you can try.

1. Handpick worms. Wait until dusk and pull worms off plants by hand. This works best after a rainstorm or thorough watering.

2. Time your watering. Cutworms don’t like to travel in dry soil, so water in the morning and lightly disturb the soil so the top dries out while moisture gets trapped beneath it. This keeps the worms underground and away from stems.

3. Boost beneficial nematodes. These soil dwellers attack and destroy cutworms. You can buy them live to introduce into your garden.

4. Spread diatomaceous earth. Pour a line of diatomaceous earth around plants to create a deadly barrier that cutworms can’t cross.

5. Try pesticides. Some gardeners have luck controlling cutworms by spraying pesticides like Bt at weekly intervals while their seedlings emerge. Regular application is necessary because the spray will wash off quickly. However, since cutworms spend most of their time underground, pesticides are often unsuccessful.

6. Remove Mulch. Don’t use mulch where you have infestations to reduce habitat space for the worms.

7. Make your plants less appetizing. A regular wash of dish soap on your seedlings is a nontoxic strategy to deter cutworms from attacking plants.

8. Apply bacteria. Bacterial treatments like Bacillus thuringiensis can kill off young larvae before they cause damage.

Preventing Cutworms for the Long Term

The best way to keep your plants safe from cutworms is to avoid introducing them in the first place. Here are strategies for preventing this pest population from getting established:

Maintain a 4-foot barrier of open dirt between your lawn and your garden to prevent cutworms from traveling over.
Till in the spring and fall to kill some of the cutworms that have overwintered and expose the larva to birds and other predators.
Plant mustard, sunflowers, lamb’s quarters, and quack grass far from your garden, surrounded by pheromone moth traps. They will attract and trap the adults before they can lay eggs.
Incorporate birdhouses and bat boxes into your garden space so these natural predators can feast on cutworms.

Keep Cutworms Out of the Garden for Good!

By following these prevention tips, you can help keep cutworm populations under control and lessen the risk of these tiny caterpillars taking over your garden. It takes diligence and lots of observation to keep these insects in check, but the results for your garden are well worth the effort.