What Are Cutworms And How To Get Rid Of?

Cutworms are the larvae, or worm stage, of several moth species that live in the top inch or two of soil to feed at the base of plant stems. There are numerous varieties, and appearance varies between them. The commonly occurring cutworms are turnip moths, large yellow underwings, and black cutworms. These look similar as they have greyish-brown, pale green, or creamy-white bodies, three pairs of legs at the head end, and five pairs of clasping prolegs on their abdomen. 

Adult moths lay eggs on plant debris during the summer. The cutworm eggs pupate in the autumn or overwinter, complete their feeding in the soul, and reemerge the following spring. Both adult moths and larval cutworms are primarily nocturnal; however, the adults feed on plant nectar, while the caterpillars feed on various plants, like brassicas, nightshades, beans, and sometimes turf grass.

Small populations of cutworms can do a little harm, but a large one can decimate an entire vegetable garden. They feed on plants at the soil line, which makes it look like they have been cut right through the base, causing them to topple over. They also nibble on growing plant shoots on the upper portion of plants, leaf petioles, and plant roots. 

Cutworm activity is high at the start of the season, but some of its species persist actively over summer and autumn. Their damage is confused with that of slugs and snails, puzzling both gardeners and farmers. However, the holes caused by cutworms are typically smaller than slugs and snails, which also leave behind silvery slime trails.

The most common signs of cutworm activity include:

• Transplants and seedlings with damaged stems cut off at the soil line
• Outdoor seedlings and transplants that wither quickly, even when watered thoroughly
• Young seedlings that disappear overnight
• Healthy plant leaves clipped off without other signs of damage
• Holes and cavities bored into tomatoes, potatoes, cauliflowers, and other crops
• Cutworm frass beneath affected plants

Cutworm damage can be devastating, so it is better to check susceptible plants frequently and take action before it is too late. 

1. Handpick Cutworms

Handpicking cutworms is neither the most pleasant nor the easiest experience. It is, however, quite effective, especially in the spring. Since these worms are active at night, the best time to go hunting with flashlights and gloves is during the evening or after dark. Scan around the base of damaged plants or dig down a few inches in the soil. 

When disturbed, the worms curl into a C-shape, so if you spot anything similar, pick them out and drop them into a bucket of soapy water. Repeat this every few nights to control their population. Early detection can help prevent severe damage, so monitor the garden regularly and handpick them as soon as you spot them. 

2. Use Protective Plant Collars

Cutworms wrap around the plant stems to munch it off. To prevent this from happening, you can plant collars. Plant collars made of 4-inch-long cardboard pieces, toilet paper rolls, or aluminum foil extended 1 to 2 inches into and 2 to 3 inches above the soil to loosely encircle plant stems. This human-made barrier protects the seedling stems, preventing cutworms hiding in the soil from destroying young plants. 

These protective techniques work best for recently transplanted seedlings. You can remove them when the seedlings are well-established and the cutworms are less active later in the season.

3. Stem Protectors

Another tactic to stop cutworm damage is placing a nail, plastic drinking straw, or wooden stick right next to the stem. The idea is to put something tall around the plant stem to prevent the cutworm from wrapping around and cutting it. The object should be at least 2 inches above the soil, as cutworms attack low on the stem. 

This technique disrupts the cutworm's ability to wrap its body around the plant. When it cannot encircle the stem, it cannot grip the plant effectively to feed. You can use this method with plant collars for added protection.

4. Experiment with Companion Planting

An essential tool in organic gardening is companion planting with the right plants to help reduce the cutworm population and keep your garden pest-free. Among these plants, marigolds would be best used alongside a more vulnerable vegetable type like tomatoes and lettuce, for their scent is aversive to cutworms.

You don’t have to limit yourself to marigolds. Planting flowering herbs like dill, cilantro, or parsley near your crops is just as effective. The herbs attract predatory wasps and other insects that feed on cutworms and cut down their populations at the same time. This approach protects your crops and supports the health of your soil and surrounding plants. 

5. Plant Sunflowers

Plant sunflowers at the periphery of your garden as trap crops. This works because cutworms love sunflowers, prioritizing them over a plethora of other vegetable crops. These flowers are an excellent bait to lure the larvae away from your main garden. 

They will attract the larvae, giving you a chance to pick them from the ground before they even get the opportunity to migrate to your valuable crops. Once you spot the worms on the sunflowers, you can handpick them off your plants.

6. Attract Natural Predators

Cutworms are not exclusively preyed by insects; wild birds also hunt and consume them. To attract various birds, like robins, chickadees, and sparrows, consider installing bird feeders filled with grids of seeds or suet or adding a nearby bird bath or water feature with a constant water source near your garden. 

These birds will hover over your flower beds and gorge themselves on any cutworms or other pests they come across. To maximize effectiveness, position feeders and water sources near vulnerable plants but away from areas where birds might damage crops. 

7. Tilling the Soil

Another way to lure wild birds to your yard is to till the soil and expose the cutworms hiding in soil patches beneath grass clippings or debris from dead plants. During tilling, their habitat is disrupted, bringing the cutworms to the surface. 

Exposing the cutworms makes them easy prey for birds such as killdeer, sparrows, starlings, and robins that are attracted to gardens where food is plentiful. This method is most effective early in the spring before the crops are sown. It helps control the cutworm population when the infestation is severe and aerates the soil, improving its health and readiness for planting. 

8. Delay Transplanting

After a long winter, the cutworms wake from their dormancy and reemerge in early spring to feed on tender young seedlings. These pests are most destructive at this time because newly sprouted plants have tender, vulnerable stems, which cutworms easily chew through, often severing the plant at the base. 

One effective way to minimize damage is to delay transplanting vegetables into outdoor beds by a few weeks. This delay allows the cutworm population to decline naturally since they become less active and transition to their next life stage. Additionally, slightly older and more established plants are challenging for cutworms to damage because their stems are thick and tough.

9. Avoid Using Mulch 

Organic mulch is helpful to plants during winter but not so much in your battle with cutworms. Cutworms hide beneath the mulch during the day. Therefore, avoid using mulch and instead use a technique called dust mulching between plant rows to prevent cutworm activities. Dust mulching is when you till or hoe the soil up to an inch of shallow depth to create a dry, loose, and fluffy surface. 

Cutworms cannot crawl across or find shelter in this soil texture because they need a moist, compact environment for movement and survival. The dry surface also exposes the larvae to predators and harsh environmental conditions, reducing their numbers even more. Additionally, dust mulching enhances soil aeration and prevents weed growth, further deterring pests.

10. Diatomaceous Earth

Physical removal and garden maintenance are enough to manage cutworms, but if you have to resort to pesticides, choose organic options like diatomaceous earth (DE). DE is one of the most recommended natural remedies for any pests, including cutworms is less damaging to pollinators. 

Diatomaceous earth is the fossilized, abrasive remains of prehistoric sea life that you can sprinkle in the soil and is deadly to any larvae that crawl over. Spreading a line of DE around the base of plants sets up a barrier to larvae.

11. Bacillus Thuringiensis

Another approach is Bacillus thuringiensis (Bt), a naturally occurring bacterium common in some soils that targets many caterpillar-type pests. It contains an active ingredient, a crystal protein that paralyzes insects’ digestive systems. The infected insect stops feeding and dies from starvation or a ruptured stomach. 

For optimum results, spray the BT on affected plant leaves and avoid irrigating for two days after treatment. When applying BT, ensure you have the right strain for the pest you want to control. The cutworm should also be in the larval stage. Lastly, remember to follow the label directions.

12. Nematodes

Releasing beneficial nematodes in moist spring soil that feed on cutworms is another natural biological control option. They’re especially effective when applied during the season after cutworms have been a problem. For maximum effectiveness, the nematodes should be watered in moist soil immediately after purchase when soil temperature is around 12-20ºC. This temperature range usually occurs between April and September. 

Nematodes should be applied following the suppliers’ instructions immediately after purchase. You should water the soil before and after application to ensure it is sufficiently moist for nematode activity and survival. Repeat applications may be necessary.

13. Water in the Morning

Morning watering reduces damage from cutworms. When you water early, the moisture will dry up just in time before the worms, which prefer moist conditions, start feeding in the evening when they are the most active. Dry soil is challenging for them to move around and feed on your plants. 

Besides, early watering gives the plants a good chance to replenish moisture, so they can absorb all of it before the day’s heat causes evaporation, leaving them refreshed and healthy. Also, healthy, well-watered plants are more resistant to pest damage since they can heal from minor feeding injuries more effectively

Your lawn, yard, or garden cannot be pre-treated for cutworms because no chemicals or pre-treatments for these pests do not exist. However, here are some things you could do to limit or stop their damage before there is devastation in your garden or lawn.

Keep Gardens Tidy

Cutworms can overwinter as larvae or pupae in old plant debris, so thoroughly clean your garden in the fall to prevent an infestation during the growing season. Destroy any infected plant matter by burning or bagging it and throwing it in the trash to deprive the worms of their overwintering sites. 

Once spring sets in, plant a different crop over cutworm-damaged areas from the previous year, thus breaking their life cycle. You may want to consider using a floating row cover on newly germinated seedlings for protection against cutworm moths landing on defenseless vegetables to lay eggs.

Control Thatch

During the daytime, cutworms hide from predators and environmental stress in layers of thatch layer. For the unversed, thatch is the layer of dead grasses, roots, and organic material that develops between the soil surface and living grass. As the thatch layer becomes so dense, it creates a perfect environment for cutworms to hide and thrive.

Therefore, dethatching, the process of removing the layer of dead materials, is crucial to prevent infestations. It can be done physically by raking or using specialized dethatching devices to disrupt the cutworms’ hiding spots. A thinner thatch layer facilitates aeration, moisture penetration, and nutrient uptake in your lawn, promoting healthier grass growth with fewer pest threats.

Create Bare-soil Strip

A bare soil strip (or more)between your lawn and garden plants acts as a physical barrier to prevent the cutworm larvae from moving from the lawn to your plants. This cleared section of soil free of vegetation limits the larvae’s access to food sources and reduces their movement opportunities. Additionally, this open space provides a clear, visible zone where you can spot and address pest problems early.

It is advisable to make a soil strip at least 3 feet wide. Clear grass, weeds, and other plants from that strip using a hoe, shovel, or weed killer. Then, loosen the topsoil in that area to a depth of 2 to 3 inches using a garden tiller or hoe to break up compacted areas.