Cutworms

How to Identify and Get Rid of Cutworms

black-cutworm-control-prevention

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

GrowVeg.com/Sam Droege on Flickr Creative Commons

Cutworms can be a major annoyance in the garden, particularly for young seedlings or transplants. Here are tips on how to identify, control, and get rid of cutworms.

What are Cutworms?

“Cutworm” is the name used for the larvae of a number of species of adult moths. Eggs that hatch in the fall can produce larvae capable of overwintering in the soil or a woodpile. They do the most damage early in the gardening season, when they emerge from hibernation. 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 are common on a wide variety of vegetables and any fresh seedlings. To identify them, try patrolling your garden in dusk and evening hours, when cutworms will begin to feed. They are also partial to cloudy days.

Different species range in color from grey to 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, while hiding in daylight hours.

Black cutworms, also known as Agrotis ipsilon, are some of the most common cutworms. They have small dark spots on their bodies and mature into the dark sword-grass moth. Variegated cutworms, another common species, 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 they are about 1 ½ inches long with a 1 ½-inch wing length. You should keep an eye out for them, because the females will lay eggs in dry soil after they mate.

brown-cutworm-moth-identification.jpg
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.

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 damage.

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

Control and Prevention

How to Get Rid of Cutworms

  • Make plant collars. Put a 4-inch piece of cardboard around each plant stem to help stop cutworms from reaching tender stems, especially right at transplanting. This time-consuming task works, though it is only efficient for a smaller garden.
    • Or, try this method: Save toilet paper tubes, cut them in half, fill with potting soil, and stand up in a tray. Use for planting seeds. When young plants are ready, plant them, tube and all. 
  • Hand pick. Go out at night with a flashlight and gloves. Pick off the cutworms and drop into soapy water; repeating this every few nights.
  • Sprinkle used coffee grounds or egg shells around your plants.
  • Circle stems with diatomaceous earth, a natural powder made from ground up fossils which kills insects when they walk over it.
  • Apply an insecticide late in the afternoon for best control. Some readers use Bacillus thuringiensis, a natural way to kill cutworms. However, note that this bacterium may harm butterflies, an important pollinator.
  • 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

  • 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.
  • Fireflies are a fun insect to have around the garden, plus they are a natural predator to cutworms. Check out these tips to attract fireflies to your garden.
  • Birds are another natural predator to cutworms. Learn how to make your garden bird-friendly.

Reader Comments

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Cutworms: You say, "apply

Cutworms: You say, "apply insecticide". Plz name one or more commercial insecticides that I can purchase. Thank you.

You'll need to contact your

The Editors's picture

You'll need to contact your local garden center as insecticide usage and laws vary by state or province.

A neighbor of mine is having

A neighbor of mine is having trouble with cutworms coming into their house. She said they're even in her cabinets. What can she do? It isn't safe to put insecticide inside her place or her cabinets.

We've never experienced

The Editors's picture

We've never experienced cutworms in the home (only in the garden). We wonder if it's a different kind of worm?  See this page for reference: http://www.ext.colostate.edu/p...

They have been coming in our

They have been coming in our house and they're definitely cutworms. We see them in the garden too. They're coming under the door (need to get better weatherstripping!). They seem to love burrowing in our carpet to pupate. Ugh!

Hmm. Whether cutworms or

The Editors's picture

Hmm. Whether cutworms or another chunky caterpillar, that is certainly unpleasant. We'd definitely suggest getting better weatherstripping under the door, and perhaps a draft dodger might help as well. You might also try sprinkling regular clay cat litter along the outside of the door threshold to deter caterpillars from crawling inside--the caterpillars may not like the gravelly texture. (Coffee grounds or egg shells might attract other pests to your home. Diatomaceous earth, a fine powder used as a control for caterpillars, may track in more easily and possibly cause respiratory problems to people or pets who might be senstive.)
As for when they get inside the cupboards, if you don't think it would cause other pest problems, you might set a plastic plate of molasses in a section of the cupboard--this is said to act as glue to a caterpillar. Monitor every day and replace as needed.
You might also be interested in this page, where someone had a similar problem (no solution, however):
http://bugguide.net/node/view/...

I had cutworms in my yard.

I had cutworms in my yard. The way they come inside the house is because they attach to your clothes if you walk through the grass before coming inside. Before entering the house check the bottom of your pants and shake them off.

I have these cutworms in my

I have these cutworms in my petunias in my window boxes and they are doing a number on them. It will get down to 40* tonight, do you think that will affect them? Or do I need to get some insecticide/used coffee grounds? Please help

40 degrees Fahrenheit would

The Editors's picture

40 degrees Fahrenheit would probably not affect cutworms. Black cutworm eggs, for example, can withstand several hours exposure to freezing temperatures. We'd suggest putting cardboard collars or tin foil around the base of your plant stems, especially if they are young. Also sprinkle used coffee grounds and/or diatomaceous earth. You can also gently dig around the base of plants to locate any cutworms in the soil and remove them.

I have cabbage tomato and

I have cabbage tomato and different pepper plants together we jist had several rain storms I have to different pepper plants wilted really bad what can I do

The heavy rain could have

The Editors's picture

The heavy rain could have caused the peppers to wilt a bit. They don't like to sit in wet soil. Wait a couple of days to see if they will perk up. If not, check for bugs.

We have 6 tomatoe plants in a

We have 6 tomatoe plants in a row. They are 2or3 foot apart from one another. There is 1 in the crowd that is dying. We put miracle grow on them. We have cages around them. That one is dyin. Why?

Hi Joanne, There could be a

Celeste Longacre's picture

Hi Joanne,
There could be a lot of reasons why one plant is dying. However, if it is cutworms, you need to protect the rest of your plants. I use tin foil and place a 2 inch strip around the base of the plant with 1/2 of it above and 1/2 of it under the soil.

We wrap rhubarb leaves around

We wrap rhubarb leaves around our tomato plants after they are transplanted and have had great success with it. Slit a leaf,then wrap it so there is no room for the cut worm to crawl through I put soil on the leaves to keep them in place they also help keep the moisture in.

mine are in high desert and

mine are in high desert and have apperance of white worm the neighbor edentifyed as red head is "CUT WORM" i also hurd if planting a six pack tomato can be wraped with alumium foil to prevent worms from eating!

Hi Juju, See above.

Celeste Longacre's picture

Hi Juju,
See above.

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