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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

<a rel="nofollow" href="http://almanac.com">Taseer Hassan</a> Mon, 03/21/2016 - 12:40
I have lots of CUTWORMS in my home. Please help me in solving these problem. They are spreading everywhere in my home. They are making nest on walls of my home. I am very in problematic situation.
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 03/24/2016 - 14:29

Hi, Taseer: Cutworms live in soil, so you will want to make sure that you minimize whatever dirt may be inside your house, including in plant pots. If indeed you don't have cutworms but instead some other sort of caterpillar, then the trick is to find out how they are getting in (or got in, to lay their eggs). If you can figure out where their nests are, sometimes it's possible to insert a shop vac (even if you have to create a temporary hole, but be careful about electric lines) and suck out the nests. Unfortunately, the best remedy is simply to remove them as they emerge, but the key thing to all of this is to seal your walls, including the bottoms. Good luck!

 <span>Judy T</span> Thu, 07/09/2015 - 09:48
Something has eaten the bark of a tomato plant and left white film on the bottom of the stem. What is this and how can I treat it?
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 07/13/2015 - 10:45

If it is cut worms you can try some of the tips above. Make collars out of paper or cardboard and put around the stems. You can also try to spray the plant with insecticidal soap spray (a few drops of dish soap mixed into a quart of water).

 <span>Davidgh</span> Sun, 06/28/2015 - 23:49
I have some young (less than a year old) citron plants and today I discovered that a pest has eaten the leaves from the outside in and it has eaten the outer stem of some of these plants while leaving the core stem intact. Please help me figure out what kind of bug this is and how to get rid of it!
<a title="View user profile." href="/author/editors">The Editors</a> Wed, 07/01/2015 - 14:06

Citron is attacked by many of the common citrus pests. Could it be that two pests are attacking your plants? Such as grasshoppers or orangedog caterpillars on the leaves and rabbits or rodents girdling the trunk? Depending on where you live, pocket gophers, ground squirrels, voles, etc., may chew the bark and girdle the tree. See below for some common citrus pests and how to control them. Good luck!

http://www.ipm.ucdavis.edu/PMG/C107/m107apyoungtrees.html

http://edis.ifas.ufl.edu/ch056

http://edis.ifas.ufl.edu/cg005

 <span>Dwain</span> Wed, 06/24/2015 - 12:00
The stems and leaves on the lower part of my tomato plants are dying. Is this the sign of cutworms? I have not seen any.
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 06/25/2015 - 10:58

No, it sounds if you have "early blight" which is caused by a fungus. Avoid splashing any water on the leaves. Irrigate at the ground level and do not water from overhead. Remove any plant debris. Remove leaves in the lower 8 to 12 inches of the plant. Get rid of all the infected plants parts. If caught early, get a fungicide from your garden center to spray your plants, as directed.  See more about growing tomatoes on our "Tomato" page here: www.almanac.com/plant/tomatoes

 <span>Lynn P.</span> Mon, 06/22/2015 - 21:49
I have cucumber and cantaloupe seedlings that have been outside for a couple of weeks (zone 5) and suddenly I am finding them cut off cleanly about 3" above the ground - a couple of plants each night. I didn't suspect cutworms because the plants are large (trailing a foot or more now), the cut lines are high and I thought that it was too late in the season. Didn't find any cutworms on a search tonight. Could it be cutworms after all - or something else? Thanks very much for any advice you can offer.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 06/23/2015 - 11:56

It could be that an animal is munching on your seedlings, such as a rabbit, squirrel, deer, or groundhog. Rabbits tend to cut off vegetation cleanly, while deer damage might be more ragged. If you suspect an animal pest, you might try installing a motion-detector sprinkler.

For more information, see:

https://extension.umd.edu/growit/leavesstems-chewed-vegetable-seedlings-and-transplants

http://theiowagardener.com/What%27s_eating_my_plants.html