Cutworms

Updated August 2026 · Garden Advice Guide

A seedling that was fine last night and is lying on the soil this morning, cut through cleanly at the soil line with the top still green and untouched, was killed by a cutworm. A physical collar around the stem stops them completely, and a toilet paper tube pushed an inch into the soil is as good as anything you can buy. For most gardeners that one fix ends the problem for the whole season.

The collar has to be in place the day you transplant, not the day after you lose a plant. Work out your bed layout and how many transplants you need with our free plant spacing tool, then cut that many collars before you take the tray outside.

Updated August 2026

Cutworm Control, in the Right Order

1. Cultural. Keep beds weed free for two to three weeks before planting, remove crop debris, and transplant slightly older, thicker-stemmed seedlings rather than the thinnest ones in the tray.
2. Physical. Collars on every transplant, evening handpicking, and turning the soil to expose larvae before planting.
3. Biological. Beneficial nematodes watered into moist soil, plus the ground beetles, birds, and parasitic wasps already living in your garden.
4. Chemical, last. Only for a severe, confirmed, repeat infestation, using a product whose label lists cutworms and your crop.

The reason chemical control sits so far down here isn't squeamishness. It's that cutworms spend the day underground and the night at the soil surface, so foliar sprays mostly miss them, and a two-cent cardboard tube achieves what a spray can't.

What Cutworms Actually Are

Cutworms are the caterpillar stage of several night-flying moths in the family Noctuidae, the same family as armyworms. The black cutworm, Agrotis ipsilon, is the one behind most transplant losses in North American vegetable gardens, but the variegated, dingy, and bronzed cutworms all do the same job.

A full-grown larva is 1 to 2 inches long, fat, smooth, and greasy-looking, in gray, dull brown, dirty greenish, or nearly black, sometimes with faint stripes or a speckled pattern. There is no hair and no bright color. It looks like a piece of animated cooked spaghetti in a bad mood.

The behavior that identifies them: when you touch one, it curls into a tight C. Every time. That single reflex separates a cutworm from a wireworm, a millipede, or a grub in about half a second.

The adults are drab brown moths that fly at night and are drawn to lights. The females lay eggs in low grassy areas, on weeds, in crop residue, and on the soil surface, often hundreds at a time. In much of the country the black cutworm doesn't overwinter in cold soil at all; the moths migrate north on spring storm systems, which is why some years are terrible and others are quiet in the same garden.

Larvae feed for three to five weeks, then pupate in the soil. Most home gardens see one damaging generation in spring and sometimes a lighter second one in mid to late summer.

Where Cutworms Hide During the Day

This matters because it's how you catch them, and it's also why sprays underperform.

Cutworms feed after dark, sever a stem, often drag a bit of it under, and then retreat before dawn. They do not go far. A cutworm that cut a plant last night is almost always within 2 to 4 inches of that plant, curled up in the top inch or two of soil. They favor the shady side, under a clod, under mulch, under a leaf lying on the surface, or right against the stem base of the plant next in the row.

Here's how to find one, and it works about eight times out of ten:

1. Go out in the morning, as soon as you find a cut seedling.
2. Kneel at the cut stem and scratch the soil around it with your fingers or a hand fork. Go about 1 to 2 inches deep and work out to a 4 inch radius.
3. Turn the loose soil over as you go and look for a smooth gray or brown grub. Check under any clods and under the mulch layer specifically.
4. Touch anything that looks like a candidate. If it curls into a C, that's your culprit.

Drop it in soapy water, or leave it on a path for the birds. One cutworm can take out several seedlings across successive nights, so finding it is worth ten minutes.

The second way to find them is the flashlight patrol. Go out an hour or two after full dark with a flashlight and look at the soil surface right around your transplants. They'll be out feeding. This is by far the most reliable method when you have a real infestation, and twenty minutes on two consecutive nights usually clears a small bed.

Cutworm Collars: The Fix That Actually Ends It

A collar is a physical wall the larva cannot climb over or tunnel under. It doesn't repel, kill, or deter anything. It just makes the stem unreachable, and cutworms are not persistent problem solvers.

What to use, ranked by how well it holds up:

• Cut aluminum or steel cans, both ends removed, roughly 2.5 to 3 inches tall. Last for years, reusable, and completely rigid. The best option if you have the cans.
• Toilet paper and paper towel tubes, cut in half for toilet rolls or into thirds for towel rolls. Free, fast, and biodegrade by midsummer, which is exactly when you no longer need them.
• Stiff cardboard strips from a shipping box, cut 4 inches by 8 inches and stapled or taped into a ring. Good when you need a wider collar for a big transplant.
• Cut plastic cups or yogurt pots, bottom removed. Durable, but they trap heat against the stem in hot climates and can hold water, so lift them once the plant thickens.
• Sections of PVC or old hose split lengthwise, useful for a few high-value plants.

The three measurements that make a collar work:

1. Sink it 1 to 2 inches into the soil. This is the part people skip, and it's the part that matters. A collar sitting on the surface is a ring the cutworm walks under. Push it down until it's clearly anchored and firm the soil against it on both sides.
2. Leave 2 to 3 inches standing above the soil. Cutworms don't climb well, and two inches of smooth wall stops them.
3. Leave about half an inch of clearance around the stem. Snug enough that there's no wide gap of open soil inside, loose enough that the stem can thicken without being girdled. For a pencil-thick tomato stem, a toilet roll tube is close to perfect.

When to remove them. Once the stem has gone woody and is thicker than a pencil, usually three to four weeks after transplant, cutworms can no longer cut it. Cardboard collars can stay and rot. Cans and plastic should come off so they don't restrict the stem or hold moisture against it.

One warning worth stating plainly: a collar protects the stem, not the plant. Climbing cutworm species will go up the outside of a collar and chew leaves and buds. That's a much smaller problem than a severed stem, and it's rarer, but if you're losing foliage rather than whole plants, collars won't be the answer.

Other Cutworm Controls, and How Well They Work

Evening handpicking. As covered above, this is the most effective non-collar control there is. Flashlight, an hour after dark, two nights in a row. It's tedious and it works.

Turning the soil before planting. Cultivating a bed 2 to 3 inches deep about two weeks before you plant does two things: it exposes larvae to birds and to drying, and it kills the weed seedlings they were feeding on. In practice, robins and blackbirds will follow you down the row. This is genuinely useful, but it's a numbers reducer, not a guarantee.

Keeping the bed weed free for 2 to 3 weeks before planting. This is the most underrated cutworm control in the book. Moths lay eggs on weedy, grassy ground, and larvae that hatch there are already in place when you plant. A bed that has been bare and clean for a couple of weeks starves out the larvae already in it, because they have nothing to eat until your transplants arrive. If you are converting lawn or a weedy patch into a vegetable bed, expect a bad cutworm year and collar everything.

Beneficial nematodes. Steinernema carpocapsae is the species to look for, because it's an ambush hunter that patrols the top layer of soil, which is exactly where cutworms are. Water it into moist soil in the evening or on a cloudy day, since UV light and dry soil both kill nematodes fast. Soil needs to be above roughly 55 to 60°F for them to be active, and the ground has to stay damp for a couple of weeks afterward. Applied properly, published suppression figures generally land in the 50 to 80 percent range, which is a real reduction but not a wall. Applied to dry soil in full sun, results are close to zero, and that's why so many gardeners say nematodes didn't work for them.

Bt, with an honest caveat. Bacillus thuringiensis subspecies kurstaki is a bacterial product that kills caterpillars and nothing else, which makes it about as selective as pest control gets. Cutworms are caterpillars, so in principle it should work.

In practice it often doesn't, for a simple mechanical reason: Bt only works when the caterpillar eats it, and cutworms spend the day buried and feed at the soil line at night. Very little of what you spray on foliage ends up in a cutworm. It also breaks down in sunlight within a day or two.

Where it does help is with climbing cutworms feeding on leaves, and there the trick is to spray the foliage and the soil surface in the late evening so the residue is fresh when they come out. Treat Bt as a partial measure worth trying on a bad infestation, not as your plan. The collar is the plan.

Diatomaceous earth and cornmeal. These come up constantly in gardening forums. Diatomaceous earth has some abrasive effect on soft-bodied larvae while it's bone dry, but it stops working the moment it gets wet, which in a watered vegetable bed is most of the time. Cornmeal has no credible evidence behind it at all. My recommendation: skip both and spend the effort on collars.

Which Plants Cutworms Target, and When

Cutworms are not fussy. They'll take almost any young, tender, thin-stemmed plant. But the losses cluster hard in a few places.

Most at risk: tomatoes, peppers, eggplant, cabbage, broccoli, cauliflower, and other brassica transplants, plus young beans, corn, and cucumber seedlings. Anything with a soft green stem the diameter of a pencil or less.

Rarely damaged: established perennials, anything already woody, onions and garlic, and direct-sown crops past about six true leaves.

The vulnerability window is narrow and predictable. It runs from the day a transplant goes in the ground to about three to four weeks later, when the stem thickens and goes fibrous. That's it. A tomato that survives its first month is essentially immune for the rest of the season.

Two things widen that window. Transplants that were set out soft and leggy stay vulnerable longer, which is one more reason to harden properly before planting out. Our guide on hardening off seedlings covers how to get a thicker, tougher stem before the plant ever meets a cutworm. And planting too early into cold soil stalls growth, so the stem stays thin for weeks instead of days. Timing your move outdoors well matters here, and when to transplant seedlings covers the soil temperature and date targets that get plants growing fast.

Is It Really a Cutworm? Damage Compared

This table settles the four things most often confused with cutworm damage.

The single most reliable distinguishing feature is the clean cut with the top left behind. Nothing else does that. An animal that goes to the trouble of biting through a stem eats what it cut. A cutworm chews through and then feeds on a little of it in place, leaving most of the seedling lying on the soil like a felled tree.

Damping-off is the one people miss most. If the stem is still attached and just went thin, brown, and water-soaked at the base, that's a fungal problem from cold wet soil and crowding, and no collar in the world will help. That's a sowing and spacing fix.

Worked Example: Protecting a Bed of 24 Transplants

Here's a full protocol for a 4 by 12 foot bed going into tomatoes and peppers, with a history of losing three or four plants a year.

Two weeks before planting. Clear every weed from the bed and a two foot margin around it. Turn the top 3 inches of soil with a fork and rake it level. Leave it bare. Any cutworms already in the bed now have nothing to eat, and the birds will take a share of the ones you turned up.

The night before planting. Cut the collars. For 24 plants at 18 inch spacing you need 24 collars. A dozen toilet roll tubes cut in half gives you exactly 24, each about 2 inches tall. Cut them a shade taller if you can, around 3 inches, from paper towel tubes cut in thirds. Total cost: nothing. Total time: about 15 minutes.

Planting day. Set each transplant, firm it in, water it, then slide a collar over the top of the plant and push it 1 inch into the soil so about 2 inches stands proud. Firm the soil against the outside. Do this as you plant, not at the end, so nothing gets missed.

Twenty-four plants, roughly 20 seconds each for collaring, is about 8 minutes added to your planting session.

Nights 1 through 5. Go out once, on night two or three, with a flashlight, an hour after dark. Walk the bed and check the soil surface around each collar. Anything you find, remove. If you find more than three or four larvae in one pass, go out a second night.

Every morning for two weeks. Count your plants. If one is down, scratch the soil in a 4 inch circle around the stump and find the larva. Replace the seedling and collar the replacement.

Week 4. Stems should be thicker than a pencil. The cardboard tubes will be soft and starting to break down. Leave them, they'll disappear on their own.

The math on this: in a bed that historically lost 4 plants out of 24, that's a 17 percent loss, and each replacement costs you two to three weeks of harvest time on that plant. Eight minutes of collaring and one flashlight walk usually takes losses to zero or one. Very few things in a vegetable garden pay that well for that little effort.

Where Chemical Control Fits, and Its Limits

For a home garden, almost never. Collars, handpicking, and a clean bed handle this pest at a level chemicals struggle to match, because the target spends the day underground.

If you have a large planting, a documented severe infestation, and losses that collaring can't practically cover, the classes labeled for cutworms in home garden products generally include pyrethroids, spinosyns, and Bt for foliar-feeding species. Availability differs by state and changes year to year.

Read the label and follow it exactly. It lists the crops the product may be used on, the correct rate, the interval between applications, and the days you must wait before harvest. That document is the law, and no article, including this one, can substitute for it. Never use a lawn or ornamental product on food crops.

Two practical points if you go this route. Applications for soil-surface pests are made to the soil around the plants in the late afternoon or evening, so the residue is fresh when the larvae come out to feed, and the soil should be moist rather than dust dry.

Never spray a plant that is in bloom. Bees and other pollinators work open flowers through the morning, and pyrethroids and spinosyns are both directly toxic to them while the spray is wet. On a vegetable bed this rarely conflicts, because the cutworm window closes weeks before tomatoes and peppers flower heavily, but if it does overlap, apply after dark when flowers have closed and keep the material off the blossoms entirely. Losing your pollinators costs you more fruit than the cutworms ever will.

Where the sources genuinely disagree

Fall tilling. Some extension guidance recommends turning garden soil in late fall to expose overwintering larvae and pupae to cold and to birds. Other sources, particularly soil health publications, advise against fall tillage because it destroys soil structure, kills earthworms and ground beetles, and leaves the surface open to erosion. Ground beetles are one of the better natural predators of cutworms, so there's a real tension here. My recommendation: skip the fall tilling. Do a shallow 2 to 3 inch cultivation of individual beds two weeks before you plant in spring instead. You get most of the exposure benefit, in the right place, at the right time, without wrecking the bed all winter.

FAQ

What do cutworms look like?

They're smooth, fat, greasy-looking caterpillars 1 to 2 inches long, in gray, dull brown, dirty green, or near-black, sometimes faintly striped. There's no hair, no bright markings, and no legs beyond the caterpillar's normal set. The identifying behavior is that they curl tightly into a C shape the moment you touch them.

Do cutworm collars really work?

Yes, and they're close to a complete fix if you install them right. The two failure points are collars that sit on the soil surface instead of being sunk an inch or two in, and collars that go on a day or two after planting, by which time a plant may already be gone. A collar 2 to 3 inches tall, sunk 1 to 2 inches deep, on planting day, is what works.

Where do cutworms come from?

The adults are drab night-flying moths that lay eggs on weeds, grass, and crop debris, often in large batches. In the northern half of the country a large share of black cutworm moths arrive on spring storm systems rather than overwintering locally, which is why some seasons are far worse than others. Beds converted from lawn or left weedy over winter start with the highest populations.

How do I get rid of cutworms without chemicals?

Collar every transplant, keep the bed weed free for two to three weeks before planting, cultivate the top few inches before you plant, and go out with a flashlight an hour after dark on the first two nights to handpick. If pressure is high, water beneficial nematodes into moist soil in the evening. That combination handles cutworms in nearly every home garden.

Do cutworms attack established plants?

Rarely, and not fatally. Once a stem thickens past pencil width and goes fibrous, usually three to four weeks after transplant, cutworms can't cut it. Climbing species will chew leaves and buds on larger plants, which is a cosmetic problem rather than a plant-killing one.

Will coffee grounds or eggshells stop cutworms?

There's no good evidence for either as a cutworm barrier. Both come up constantly, both are essentially free, and both are far less effective than a cardboard tube. Coffee grounds are a fine compost input and eggshells are a fine calcium addition, so use them for those reasons, not this one.

Can I plant more densely to make up for cutworm losses?

It's a tempting idea and it backfires. Crowded plants compete for light and water, hold humidity that encourages fungal problems, and produce thinner stems that stay vulnerable longer. Plant at proper spacing, which you can work out with our plant spacing tool, and protect what you plant instead.

How long do cutworms stay a threat each season?

The main damage window is the three to four weeks after your spring transplants go in, and it closes as soon as stems thicken. Some regions get a lighter second generation in mid to late summer, which matters mainly if you're setting out fall brassica transplants in August. Collar those too and the second round is a non-event.

Cutworms have a fearsome reputation for a pest that a free cardboard tube defeats. Cut the collars before you carry the tray outside, sink them an inch into the soil, and check the bed with a flashlight on night two. If you're losing seedlings before they ever reach the garden, hardening off seedlings covers the stage right before this one.

Source: University of Minnesota Extension, "Cutworms in home gardens" (extension.umn.edu). Always read and follow the pesticide label. The label is the law.