Cutworm Life Cycle: A Concise Guide to Understanding these Garden Pests

Cutworms are a common pest and a concern for gardeners and farmers alike. These soft, plump, and hairless caterpillars cause damage to a wide range of plants as they feed on stems and leaves. Their colors and markings can vary, ranging from dingy white to brown, charcoal gray, or even tan source.

There are several species of cutworms, with some native to certain areas and others migrating annually. For instance, some species, like the black and variegated cutworm, migrate into Minnesota each year, while others, like the dingy and glassy cutworms, are native and can overwinter as eggs or larvae in grassy areas source. Understanding the life cycle of cutworms is essential in developing effective pest control strategies and maintaining a healthy garden or crop.

Cutworm Life Cycle

Eggs

Cutworms lay their eggs in various stages depending on the species. Some, like the black cutworm, lay eggs in early spring while others mate and lay eggs from late summer to fall. Eggs are usually laid singly on grass blades or plant stems.

Larvae

The life cycle of a cutworm progresses through multiple stages called instars. Full-grown larvae are 1-2 inches long, hairless caterpillars that vary in color from dingy white to tan, brown or charcoal gray. Cutworm larvae, such as the dingy, bronzed, and glassy cutworms, are native to specific regions and overwinter as eggs or larvae in grassy areas, emerging in the springtime.

Pupa

When a cutworm larva is fully grown, it enters the pupal stage in the soil or inside plant material. During this stage, the larva transforms into an adult moth.

Adult Moths

Cutworm adult moths are night-flying insects with wingspans ranging from 1.5 to 3 inches. Some species, like the variegated and black cutworms, migrate into regions from the south each year, while others are native to their habitats. Adult moths are not harmful to plants, but feed on the nectar of wild and cultivated flowers.

In summary:

• Cutworm life cycle includes eggs, larvae, pupa, and adult moths.
• Eggs are laid on grass blades or plant stems.
• Some species migrate yearly while others are native to specific regions.
• Adult moths feed on flower nectar and are not harmful to plants.

Types of Cutworms

Black Cutworms

Black cutworms, or Agrotis ipsilon, are gray-brown moth larvae that feed on seedlings and transplants. They can be identified by their dark spots and their tendency to curl up into a ball when disturbed¹.

• Size: 1-2 inches long
• Color: gray-brown with dark spots
• Host plants: corn, cabbage, and other vegetables

Variegated Cutworms

Variegated cutworms, or Peridroma saucia, are gray to brown caterpillars with a distinctive white stripe along their sides². They can cause extensive feeding damage on various plants, such as:

• Vegetables
• Field crops
• Turf

Army Cutworms

Army cutworms, also known as armyworms, are notorious for their soil-surface feeding habits that damage root systems of plants. They prefer host plants like:

• Vegetables
• Grasses
• Field crops

These pests belong to the same family as other cutworms, Noctuidae, within the order Lepidoptera³.

Climbing Cutworms

Unlike other cutworms, climbing cutworms prefer to feed on higher parts of plants, like leaves and fruits. They possess a unique camouflage pattern that helps them blend in with their environment. Some of their features include:

• Brown or gray coloration
• No obvious spots
• Striation pattern on their body

Subterranean Cutworms

Subterranean cutworms usually feed on roots and underground stems, causing significant damage to a variety of plants. These root-damaging pests can be found in habitats like:

• Soil surface
• Under vegetative debris

They have a different behavior from the other cutworms, cutting seedling plants at the soil surface and pulling them into their tunnels⁴.

Comparison Table

Feeding Habits and Damage

Plants Affected

Cutworms are generalist feeders with a wide variety of host plants, including:

• Corn
• Cotton
• Sorghum
• Vegetables
• Turf

Signs of Cutworm Infestation

Key indicators of cutworm presence are:

• Chopped off plant stems
• Skips or sections of rows with damaged plants
• Curling up caterpillars when disturbed

Cutworms have three primary feeding habits:

• Surface feeders
• Tunnel dwellers
• Climbing cutworms

Surface feeders chew plant stems from the soil surface, while tunnel dwellers remain underground during the day and damage plants at night. Climbing cutworms are known for climbing up plant stems to feed on foliage.

Preventing Damage

Temperature and Moisture Factors

Cutworms experience difficulty surviving in:

• Dry soil
• High temperatures

More seed treatments and spot treatments are needed during cooler, wetter periods.

Pest Management

Effective cutworm management strategies include:

• Use of insecticides
• Release of natural enemies like nematodes
• Application of soapy water

Keep in mind that pest management practices may also affect other pests, such as leafhoppers and aphids.

By understanding cutworm feeding habits, targeting their preferred host plants and implementing preventive measures, reducing cutworm-related crop damage is achievable.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Cutmorm

Subject:  Mr. Caterpillar, WHO are YOU?
Geographic location of the bug:  San Diego, CA
Date: 04/04/2019
Time: 11:41 PM EDT
Your letter to the bugman:  My 6-year-old wants to be an entomologist when he grows up. As he puts it, “I care for the earth and small creatures!” He found this caterpillar at the park today. He eagerly consulted his beloved Southern California Butterfly/Moth Pamphlet, but this caterpillar was not pictured. I promised him I’d ask you for help!
How you want your letter signed:  SoCal Insect Hobbyists

Dear SoCal Insect Hobbyists,
This is a Cutworm, the common name for many caterpillars in the subfamily Noctuinae.  Cutworms are reviled by many home gardeners because of the manner in which the caterpillars feed.  Cutworms will cut a sprouting plant at ground level in order to feed, effectively killing newly sprouted plants and seriously jeopardizing the survival of larger plants that might be able to sprout back from the roots.  Most Cutworms develop into drab, brown moths.

Letter 2 – Calico Paint

Subject: Unknown Caterpillar
Location: Newport, Pennsylvania
September 9, 2016 2:36 pm
I have never seen this one before. Found in field of tall grass and weeds.
Signature: Jordan

Dear Jordan,
This is one of the Hooded Owlet Moth Caterpillars from the genus Cucullia, and we believe that based on this BugGuide image, it is the Brown Hooded Owlet, Cucullia convexipennis.  According to BugGuide, the caterpillar is also called the Calico Paint and “Larvae feed on the leaves and flowers of aster (Aster spp.) and goldenrod (Solidago spp.).”

Letter 3 – Cattail Caterpillar

showy fall caterpillar
Tue, Oct 14, 2008 at 7:16 AM
Dear Friends:
I found this caterpillar in a typical grassy meadow (perhaps brome grass, Bromus inermis), at the beginning of this month (October 2008). I’m sometimes able to figure out things by searching them on-line but this one stumped me. I don’t often see bright caterpillars this late in the year.
thanks,
Gavin Miller
just north of Toronto, ON

Hi Gavin,
We are surprised as how quickly we located your Cattail Caterpillar, Simyra insularis, on BugGuide. Because the caterpillar feeds on cattail, smartweed, grasses, sedges, poplar and willow, the habitat includes marsh edges, wooded riverbanks, and generally any damp area where larval foodplants grow.  The adult is also known as Henry’s Marsh Moth.

Letter 4 – Corn Earworm found on Tomato Plant

Helicoverpa zea
Location: New Jersey
July 31, 2011 8:14 pm
Hi buggy peeps!
I love your site and often rely on it to ID bugs for myself or friends.
Earlier today, I found a lovely caterpillar in the garden on one of my tomato plants. Thinking it was a butterfly, I took a few photos and rehomed it in one of our flower gardens. When I came inside, I showed the photo to friends who were alarmed that I had rescued a ”tomato worm.”
I ran outside, and promptly fed it to one of my chickens (who quite enjoyed it.) I know that you don’t endorse extermination, but perhaps this was ok because it was the ”circle of life?”
I came inside and searched online for tomato worms. It lead me to photos of green horned worms. Further searching lead me to Helicoverpa zea, which is considered a corn worm and not tomato worm.
I have two questions for you:
How did it get in my garden? We are not growing corn this year.
Is it ok for my chicken to eat this creature? I found out later that you should not feed the green tomato worms to chickens, so I got nervous about the corn worm.
Ok…I lied. Two more questions: Why is it called a worm at all? Isn’t it a caterpillar? I didn’t think caterpillars were considered worms? And… how do all of these agricultural type insects come to exist in veggie gardens? Are they always present in our yard and multiply in the right situation, or do they hitch a ride on other plants that may be brought in? The majority of our garden was started from seed here at the house.
Thanks so much for your time in reading this and the response if you are able to make one. I know you are very busy!
Hope you’re enjoying your summer as much as we are!
Signature: Annie

Hi Annie,
Thanks for your lengthy and amusing query.  We believe you are correct that this is a Corn Earworm.  It fits the description provided on the University of Florida Entomology Departments Featured Creatures website which indicates:  “The larva is variable in color. Overall, the head tends to be orange or light brown with a white net-like pattern, the thoracic plates black, and the body brown, green, pink, or sometimes yellow or mostly black. The larva usually bears a broad dark band laterally above the spiracles, and a light yellow to white band below the spiracles. A pair of narrow dark stripes often occurs along the center of the back. Close examination reveals that the body bears numerous black thorn-like microspines. These spines give the body a rough feel when touched. ”  Images on BugGuide show some of the variability.  Despite its name, the Corn Earworm feeds on numerous garden crops, leading to other common names.  According to BugGuide, the Corn Earworm is also called a Tomato Fruitworm, Bollworm, Sorghum headworm and Vetchworm, and this is explained thus:  “As its common names suggest, larvae feed on a wide range of hosts, including many field crops, hence this species has been much studied.”  Since the caterpillar is the larval form of a moth that flies, adults gain entry to gardens on the wing and the caterpillars do not have to be introduced on plants. While we have heard that chickens will not eat Tomato Hornworms because of the taste, they will eat a multitude of other insects, and to the best of our knowledge, the Corn Earworm is not toxic to them.  You did some copious research before submitting your questions, and you even took the time to learn the scientific binomial name Helicoverpa zea, which is the only true name that should be used to describe your insect.  Common names, though they are often quite catchy, would confuse scientists, especially those from linguistically diverse cultures.  The language of popular culture does not follow the strict scientific guidelines for names.  Caterpillars are wormlike, and the layperson would tend to use names that are descriptive and easy to remember, hence the name Corn Earworm to describe the caterpillar that will crawl into the ripening ear of corn to feed on the kernels.  

Letter 5 – Cutworm

What’s this worm?!!
Dear Bugman,
I found several of these 3/4-inch worms (or, yeesh, maggots?) under the geranium pots on our patio. I’ve attached photos, and the head (?) is on the darker end. The thing is translucent and I can see its innards through its skin. It moves like an earthworm, by rippling its muscles up from the back toward the head. I’m just getting into gardening and I want to make sure these things aren’t harmful to my new plants (let alone that they aren’t going to morph into something even scarier!!) Thanks so much, I love your site – even though it gave me nightmares last night! Sincerely,
Emma in Northern California

Hi Emma,
Your photo looks like a Cutworm, the caterpillar of a type of moth. There are many species. Most are general feeders. They get their common name of Cutworm from the fact that the caterpillars often eat through the stems of young plants, severing them and killing them. Just squash them.

Letter 6 – Cutworm

Underground Worm
April 6, 2010
Before I get into my letter, I’d like to just thank WTB for being such an incredible resource, so thanks! Now on to the bug.
I was in the midst of some gardening when I overturned the soil in a flowerbed and found this curious creature.
The photo shows the little thing on my trowel and it’s probably the size of my pinky.
I’ve been looking at images of meal worms and grubs, but I’m not sure they match up, but I’m no expert.
Thanks so much for your time and attention!
Yours, Tina
Ontario, Canada

Dear Tina,
Thanks for your kind letter.  This appears to be a Cutworm, the caterpillar of a Dart Moth, one of the Owlet Moth subfamilies.  Cutworms can be destructive in the garden because of their feeding habits.  Cutworms often cut small seedlings at the ground level and consume the entire plant.  BugGuide has many images of Cutworms for comparison.

Letter 7 – Cutworm

Caterpiller
Location: Okanogan, Washington
March 24, 2011 2:50 pm
Here’s a nice green caterpiller I found crawling around in the grass. I think its a cutworm as it rolled into a circle. Nice marks on his back.
Signature: Ernie

Hi Ernie,
This is a Cutworm, a generic name for the caterpillars of the Dart Moths in the subfamily Noctuinae which are well profiled on BugGuide.

Letter 8 – Cutworm

Subject: fanged moth caterpillar!
Location: southern Michigan
September 8, 2015 9:29 am
This is one scary-looking dude! Take a look at those “fangs” and that defensive posture!! Can you tell me what it is? A friend of mine found it in southern Michigan in July, and asked me to share it with anybody who might help identify it. Big thanks for everything you guys do!
Signature: LM – Michigan

Dear LM – Michigan,
This is a Cutworm in the subfamily Noctuinae, but we are uncertain of the species.  Though we believe it is not the Caterpillar of a Yellow Underwing, we think you should see the similarities to the head on this individual posted to BugGuide.  The terminal prolegs are especially distinctive.  You can try browsing BugGuide for a more specific identification.

Letter 9 – Cutworm

Subject: Surprise Tenant Larva
Location: Coryell County, TX
April 19, 2016 9:22 pm
Hello, hope you are both well.
I discovered this larva living inside one of the blooming apple-blossom amaryllis plants. Its abdomen end looks remarkably like a snake’s face to me, and its body also resembles a bird dropping when curled. It curled up when I moved it gently to the petals, and when moved back it resumed its head-down, posterior snake-face-showing stance. It has gold iridescent spots along lateral (subdorsal?) lines.
As you can see, it’s eating itself out of house and home. 😀
I tried to match it to known moths and butterflies in our county, but had no luck.
Lots of rain this week, upper 60’s and cloudy.
Thank you!
Signature: Ellen

Hi Ellen,
We believe this is a Cutworm, the caterpillar of an Owlet Moth in the family Noctuidae.  We have a difficult time distinguishing different species as so many caterpillars in this large family look so similar.  You can try browsing BugGuide to see if you find any likely candidates.  Many species are not terribly particular about what plants they feed upon, which complicates identification.

Letter 10 – Cutworm in the Snow is Winter Cutworm

January 18, 2010
Live caterpillars in the snow, New England.
Hi – I found about a dozen of these caterpillars – live caterpillars – on the top of the snow this morning.  It was a windy stormy night, temps in the high 20’s.  Most of the trees in this area are oak trees.   We are in Dover, MA, about 15 miles just southeast of Boston. Can you please tell me what kind of caterpillars these are?
Thanks,
Judy

Hi Judy,
This looks like a Cutworm, a member of the subfamily Noctuinae.  Perhaps one of our readers will have more information on what species might be found in the snow.

Comment from Karl:
It’s probably a Winter Cutworm, the common name for the caterpillar of the Large Yellow Underwing (Noctua pronuba). It’s an immigrant species from Europe that has become a pest in much of eastern North America.  According to the book, Caterpillars of Eastern North America (David L. Wagner), “The caterpillars are active during thaws throughout the winter – commonly turning up on sidewalks, sauntering into garages, or crawling along banks of snow. If someone brings you a cutworm in the dead of winter – this is it.”  There are some good photos and information at: http://www.pestid.msu.edu/InsectsArthropods/NoctuaPronuba/tabi/73/Default.aspx