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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.

Photo Credit
GrowVeg.com/Sam Droege on Flickr Creative Commons

Identify Cutworms and Cutworm Damage

Written By: Christopher Burnett Garden Writer
Pest Type
Garden Pests
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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 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).

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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 from grey, pink, green and black and can be as long as two 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 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.

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

Photo Credit: John Obermeyer, Purdue University. Black cutworms can cause severe injury to the base of plants, often killing them.
Black cutworms can cause severe injury to the base of plants, often killing them. Photo Credit: John Obermeyer, Purdue University.

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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.
  • Hand pick 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 (D.E.), a natural powder made from ground up diatoms. When insects come into contact with D.E., the fine powder gets within their exoskeleton and eventually dehydrates them.
    • Warning: Pollinators such as bees and butterflies are also susceptible to D.E., so do not use it around flowers! Only place D.E. 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, 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 sm...
Read More from Christopher Burnett

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Comments

<span>Garry Foster</span> Fri, 09/12/2014 - 14:14
it is september and the ground is full of white worms with reddish brown cutting teeth they chewed off grass roots made large gouges in my potatoes and are making a real mess are these cutworms and what kind of insecticide can i use to cover a large area
<span>Dinesh Shetty</span> Sat, 09/06/2014 - 06:48
please add more clear images of worms ....cutworms, how could we recoznize any worm ???
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 09/08/2014 - 11:16

Hi Dinesh, We've added images of the more common cutworms and hope this helps. Cutworms come in many colors; some have stripes and some have spots. You only see cutworms at night so they main way you'll know you have cutworm infestation is if your plants are literally cut off near the base of their stems. You may also see droppings nearby.

 <span>Alangalton</span> Wed, 08/27/2014 - 09:27
what can i use tokill cut worms
<span>Georgewilson</span> Wed, 08/27/2014 - 09:56
The best way to keep cutworms off your plants is to use a collar as they mention above. You could also use Bacillus thuringiensis which is available in most garden centers. You can kill the adult moths with bug zappers.
<span>Cheema</span> Wed, 07/30/2014 - 10:36
control for cutworms- you can use polytrin ,which is sprayed evening times
<span>Jenett</span> Fri, 06/13/2014 - 01:42
I have something eating the tops of my tomato plants and now they are eating the tops of my cucumber plants. It is ruining my cucumbers. They have started blooming a little. I can't find any worms on them and this is the first time it has happen to me and it isn't happening to my neighbors who also have a garden. What could it be?
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 06/13/2014 - 11:29

Some species of cutworms do climb plants to chew holes and edges of leaves. Cutworms usually feed at night--check the soil about 1/2 inch down around the base of the plants to see if there are any cutworms there. (Be sure not to disturb the roots of the vegetable plants.) As another possibility, could it be an animal, such as a rabbit? Slugs and snails may also eat leaves, feeding at night; check for evidence of slime trails, and go out to the garden at night with a flashlight to try to spot the culprit.

 <span>Joyce Fessler</span> Thu, 06/12/2014 - 16:04
I have a larvae worm, similar to a cutworm boring holes in the soil in my vegetable garden. They appear to be brown striped with a horn like head. What kind of worm are these?
<span>Mickey Anderson</span> Fri, 06/27/2014 - 10:18
Cutworms often get confused with Squash Stem Borers. From what you described, I'm pretty sure you have the Stem Borer. Stem borers not only attack squash, but can attack pumpkins as well.