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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>Mike</span> Sat, 11/03/2018 - 14:34
A couple times in the past few years, while turning the soil in my raised planters, I have had to pull out 100+ grubs from a 4x8 box. This year, I am finding a few cutworms in my planter boxes and planter pots. I have some dead patches of grass that I have dug through and not seen grubs. I am suspecting that cutworms have made their way into my garden. I typically find them by digging, not seeing them out of the soil.
<span>Ken</span> Fri, 11/02/2018 - 10:24
Hello we want to try having an experiment on using alternative pesticide other than coffee grounds, eggshells, and dipping thr cuteworms in soapy water. What can you recommend some alternative pesticide for cutworms that won't harm plants specifically we want to try it in a tomato plant. Thanks in advance!!
<span>Gayle Arnold</span> Mon, 04/29/2019 - 11:39
Leaves on my hydrangeas are being eaten. I think it is cutworm. Any suggestions in addition to above?
<span>Liz</span> Wed, 06/05/2019 - 14:25
I think my hydrangeas are being eaten by cut worm. What should I use to get rid of them
<span>Kelley</span> Fri, 09/06/2019 - 18:04
Oregon hydrangeas are being eaten too!!! Help!!!
<span>Zerayacob Tesfay</span> Mon, 07/30/2018 - 07:47
Everything you provide should have more photos for make more tangible every pest and disease .
<span>April</span> Mon, 07/16/2018 - 23:30
I HAVE NO IDEA HOW TO TREAT THIS PROBLEM....I HAVE BEEN SETTING MY ALARM EVERY HOUR TO GET UP AND TRY N KILL AT LEAST 50 IN GARAGE AND ABOUT 20 ON THE FLOOR OF DINING ROOM. ANY SUGGESTIONS?
<span>Angy R.</span> Thu, 06/28/2018 - 17:49
Here is a good one. Started my spinach in a grow flat beginning of june indoors.Transplanted them to those cardboard planter pots 2 weeks later. I set them on my patio table to get them use to the sun (1 week). I go out today and they are all chopped off. I found black cut worms in the pots. The funny thing is that I only used miracle grow veggie soil and they have had no contact with the ground and have not been outside long enough for eggs to hatch. Is it possible that the packaged garden soil is infested with them when you purchase it?
<span>Raeane Brandes</span> Thu, 09/07/2017 - 18:27
We have sections of our lawn with roots eaten by cutworms. I have been removing these sections. If I did not remove would the grass reroot? I have been putting on different cutworm killers but not sure they are working. I have also had Terminex put granular poison on lawn.
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 04/05/2018 - 12:52

This sounds more like the work of grubs, which can resemble cutworms (see above). Grubs are Japanese beetle larvae that live underground and feed on the roots of lawn grass. We have more information and some organic/non-chemical ideas for eliminating there here: https://www.almanac.com/pest/japanese-beetles And keep this in mind: If you see birds, skunks, armadillos, raccoons, or moles poking around your lawn, don't be in a hurry to shoo them away: they are probably eating your grubs.