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How to Protect Seedlings From Cutworms in the Garden

Black cutworms can wreak havoc on your garden, so learn these tips for identification and control.

Image Credit:
GrowVeg.com/Sam Droege on Flickr Creative Commons
Written By: Christopher Burnett Garden Writer

Cutworms can be a major annoyance in the garden, particularly for young seedlings or fresh transplants. Here’s how to identify, prevent, and get rid of cutworms in your garden.

What Are Cutworms?

“Cutworm” is the name used for the larvae of a number of moth species. The adult moths lay eggs on plant debris from spring through fall, with some species’ eggs hatching in spring and summer and others hatching in the fall. Those that hatch in the fall then overwinter in the soil or in a woodpile, emerging in the spring to feast.

Cutworms do the most damage early in the gardening season, when they emerge from their winter slumber and feed on seedlings. Cutworms are caterpillars, but they are often mistaken for the grubs of beetles such as Japanese beetles (which are damaging in their own right).

Identification

How to Identify Cutworms

Cutworms feed on a wide variety of vegetables and flowers, so any young seedlings or transplants will be susceptible. To identify cutworms, try patrolling your garden at dusk or during the evening and inspect around the bases of plants. They are also partial to cloudy days.

Different species range in color—grey, pink, green, and black—and can be as long as 2 inches. They can be solid, spotted, or striped. They tend be curled up when they are not on the move. Cutworms are stealthy and tend to feed only at night, hiding during daylight hours.

Black cutworms, Agrotis ipsilon, are one of the most common cutworms. They have small dark spots on their bodies and mature into the dark sword-grass moth.

Variegated cutworms, Peridroma saucia, are another common species. They are mottled brown and have a faint white stripe down their backs.

Adult cutworms are moths of dark wing colors. They are usually brown or gray and get to be about 1½ inches long with a 1½-inch wing length. Keep an eye out for the adults, because the females will lay eggs in dry soil after they mate.

An adult moth of a brown cutworm.
The adult moth of the brown cutworm is an indicator that cutworm eggs could be in your soil. Photo Credit: GrowVeg.com/gailhampshire on Flickr Creative Commons.

Identifying Cutworm Damage

Cutworms chew through plant stems at the base. They primarily feed on roots and foliage of young plants and will even cut off the plant from underneath the soil. In most cases, entire plants will be destroyed; they do a lot of damage in no time at all. Even if only the bottom of the plant is destroyed, the top will often shrivel and die.

In the summer, cutworms sometimes crawl to the tops of plants and do damage there. Be careful not to mistake this damage for slug or cabbage worm damage.

A black cutworm at the base of a damaged plant.
Black cutworms can cause severe injury to the base of plants, often killing them. Photo Credit: John Obermeyer, Purdue University.

Still unsure? Try our Plant Problem ID tool to quickly diagnose pests and diseases.

Control and Prevention

How to Protect Seedlings from Cutworms

Because cutworms can quickly do devastating damage to seedlings, prevention is key!

  • Make plant collars to protect stems. Encircle each stem with a 4-inch-tall piece of cardboard or aluminum foil to help stop cutworms from reaching tender stems, especially right after transplanting. This time-consuming task works, though it is only efficient for a smaller garden.
  • Handpick cutworms off of plants. Go out at night with a flashlight and gloves. Pick off the cutworms and drop into soapy water; repeating this every few nights.
  • Surround stems with diatomaceous earth (DE), a natural powder made from ground up diatoms. When insects come into contact with DE, the fine powder gets within their exoskeleton and eventually dehydrates them.
    • Warning: Pollinators such as bees and butterflies are also susceptible to DE, so do not use it around flowers! Only place DE at the base of plants, where pollinators won’t encounter it.
  • Apply an insecticide late in the afternoon for the best results. Some gardeners use Bacillus thuringiensis (Bt), a bacterium that affects soft-bodied insects and their larvae.
  • Try this folk advice from The 1963 Old Farmer’s Almanac:
    • A mulch of oak leaves is useful against cutworms.
    • Tansy planted near cabbages keeps them free of cutworms.
    • A hog turned into a garden in early spring will root up cutworms.

How to Prevent Cutworms Long-Term

  • In the spring, emerging cutworms will be waiting to feast on your garden. Cut off their food supply by delaying transplanting or planting by a couple weeks if possible.
  • Keep up with cultivation. The moths prefer to lay eggs in high grass and weeds. At the end of the season, plow or till the garden and mow surrounding areas to expose cutworms and destroy their winter habitat.
  • Beneficial insects, like parasitic wasps and green lacewings, will attack cutworms and other soft-bodied insects. Learn how to attract beneficial insects here!
  • Birds are another natural predator of cutworms. Attract them to your garden by providing shelter (shrubs, trees) and water (bird baths)!

Garden Pests

About The Author

Christopher Burnett

Christopher Burnett

Garden Writer

Having grown up in rural New Hampshire, Chris has a great appreciation for all things outdoors, especially when it comes to native flora and fauna.Chris is an avid gardener, maintaining a small vegeta...

Read more from Christopher Burnett

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Comments

<span>Bobbie Benge</span> Sun, 07/03/2016 - 21:58
I've read through your contents on cutworms, I believe that is what I have. We came home after being gone 4 days....early July so all my broccoli heads have produced, a few of my cauliflower, but still have the broccoli, remaining cauliflower and Brussel sprout plants growing. But these are full grown plants, no young seedlings. There were holes all through these leaves....and we plucked several dozen "green cutworms". But this was not at night...6 pm, plenty of daylight here in WY. I'll continue to look every day, but what can I do to protect my remaining plants? Fels Naptha soap solution?
<span>Wendy Howard</span> Fri, 04/14/2017 - 20:01
These aren't cutworms. I think what you had there were the caterpillars of the Cabbage White butterfly which are an extremely common pest of Brassicas. The eggs are laid by the adult butterflies on the underside of the leaves. When they hatch, the green caterpillars can quickly turn an entire plant into a skeleton.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 07/05/2016 - 10:17

Try the following: Sprinkle used coffee grounds or egg shells around your plants. Also you can circle plants with diatomaceous earth, a natural powder made from ground up fossils which kills insects when they walk/crawl over it.

 <span>A.s.</span> Mon, 06/20/2016 - 13:26
The tops of our tomatoes keep getting eaten off. It looks a lot like the work of a cutworm, but they are eaten off just below the foliage. The main stems are mostly affected, but the some of the side leaf stems were eaten off as well.I wrapped the whole stem up in tin foil right up to about an inch below the main foliage, but I went out the next day and one was eaten just above the foil. I have had cut worms before and they only ate near the bottom, but this is all the way up to under the main foliage where the blossoms start. The stem just gets bitten off, and the top is left lying there. What do you think is going on? I'd appreciate any tips to help!
<a title="View user profile." href="/author/editors">The Editors</a> Wed, 06/22/2016 - 15:51

This is heartbreaking. It certainly sounds like cut worms. Are you smoothing the aluminum? You want to create a surface that has sharp edges, a surface on which the worms will cut themselves as they attempt to cross or climb it. So crinkle the aluminum around the stem. Or sprinkle crushed egg shells at the base of the plant. Even sharp pebbles. Some people cut the bottom out of paper/plastic cups and sink the cups around vulnerable seedlings. Half-gallon milk jugs from which the bottom and tops/necks are removed fit easily over larger plants. Others use (paperless) toilet rolls, but plants have to be small for those to fit.

We hope that helps!

 <span>Tiggie King</span> Sun, 05/22/2016 - 09:44
My moringa tree has ten pods and no leaves. It is about six feet tall. Why won't leaves grow? Now my corn seeds need help.
<span>Jim Gruber</span> Sat, 05/21/2016 - 20:13
We live just south of Ocala and recently began to see our lawn start to die out. I found what looks to be a cutworm in the grass while raking the dead grass out of the yard. Could these worms be doing this kind of damage to our yard? If so, I will give these remedies a try.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 05/24/2016 - 15:05

Cutworms and army worms can damage a lawn. If you identified the worm (or worms) as cutworms you can try some of these remedies. It's important to keep your lawn healthy. A healthy lawn will withstand a cutworm attack.

 <span>Tom Galloway</span> Mon, 04/18/2016 - 06:21
Thanx for the idea for getting rid of cut worms
<span>Heather Griffiths</span> Sat, 04/16/2016 - 09:22
We live in Kommetjie, a little seaside village. I have lovely pots either side of the front door and planted white roses which have not been looking good (leaves dry out and brown) and thought I it was just because everyone says roses dont like sea air. Today I turned the soil in the pots and discovered thick fat worms everywhere which I think are cutworm!! How do I get rid of them? Should I just empty the pots and start again?