Cutworms are larvae of of a large family of dull-colored, night-flying moths of several different species. They are often visible around lights in spring.
They come in various colors, but are generally a dull gray and well camouflaged within the soil. They are soft-bodied, hairless caterpillars that curl up when touched. Fully grown, they are less than 2 inches long.
Their life cycle consists of egg – larva- pupa and adult. One generation is produced each year. Eggs overwinter on the tip of grass blades or on the top layer of soil.
Army Cutworms (Armyworms) travel in great numbers. They could be grey, brown or black, striped, black sided, yellow-headed and greasy.
They hide under the soil surface during the day, but are voracious night feeders. On top of the soil they cut through seedlings or devour leaves, leaving only the stem. Some varieties infest Fruit Trees, Vines and Berry Bushes. A few varieties feed on roots causing plants to wilt and die.
Cutworm Damage
Usually larvae chew young plants off at the base at or near ground level. When you see a freshly severed plant, carefully stir the soil around it and you can usually find and destroy the culprit before it can move to the next plant.
Sometimes you will find more than one cutworm in the immediate area . Plants are often cut off completely at or just below the soil surface giving the appearance of a freshly mowed lawn
The favorite garden menu of cutworms consists of Corn, Tomato, pepper, cabbage, peas, beans, and squash. They also feed on Potatoes, Cauliflower, Misc. greens, Melons and Onions. They avoid plants with woody stems.
Knowing the signs of a cutworm infestation is the first line of defense. Cutworms are nocturnal, you won’t see them during the day. Generally the first sign of a cutworm problem is the evidence of their smorgasbords you find the morning after, and there is no morning after pill. Detecting the cutworm population explosion early will help save your harvest.
Look for Plants that are wilting or damaged, this alone could be a sign of a myriad of plant disease and insects, not necessarily cutworm – but it is indicative that you have an issue in your garden. You can find cutworms by overturning the soil by hands in the area of the damage.
Look for Cutworm droppings. They look like miniature rodent feces droppings and can be found on foliage as well as the ground, you’ll need a keen eye to spot them, but they are visible.
Handpicking cutworms off your plants at night is feasible. You’ll need a light source, then simply pick them off and squash the little buggers, a bug genocide. You can also place them in a pail of soapy water to drown. You’ll need to repeat this a few times weekly. Even if you think you have them beat you should keep checking throughout the season for a reemergence.
Plant collars.
Cutworms will eat plants by chewing near the plant base through the stems, Placing barriers around the stems will slow them down, and in most cases stop them.
Cardboard tubes from paper towel or toilet paper rolls work for this, but tend to disintegrate after repeated rain and watering. Plastic bottles or metal cans with the ends cut off work even better.
Collaring is only feasible if you have a small garden, or a lot of time and patience. Every stem will need a collar , if the cutworm is turned away from one plant they’ll go to the next , so basically deterring from one plant simply detours then to another.
Place the plant collars around the plant stems and push them down into the soil about an inch, leaving the collars about 3 inches in height. If you fashion your collars from cardboard or plastic, be sure that the seam is securely fastened so that cutworms can’t crawl through it.
A plastic drinking straw of adequate girth and length with a slit cut lengthwise placed around the base of plants and pushed into the soil slightly will not only bolster the plant , but act as a shield against cutworm attack.
Using Natural Deterrents and Pesticides
Bt Bacillius thuringiensis is a bacterium that is known to kill cutworms, and is readily available to home gardeners. It’s harmless to people and pets. Apply it to the soil in the affected area at either bloom or petal fall, or both.
Bt is not generally harmful to beneficial insects. It is a stomach poison and must be ingested . It is more effective when applied during warm, dry weather while the larvae are actively feeding.
As cutworms are nocturnal an early evening or late afternoon application is best. Bt breaks down quickly in nature so more than 1 treatment per season is necessary.
Diatomaceous Earth
It’s harmless to pets, people and plants but kills soft bodied insects, such as cutworms, that tread over it by piercing them and causing dehydration. Finely ground eggshells will work as well, be sure they are clean shells , no egg residue, as this can lead to other problems.
I’ve heard garden gurus suggest a molasses treatment. Mixing molasses with sawdust and wheat or corn bran, and applying it around plants. I can’t attest to whether it worked on the cutworms or not, but when I tried it a while back the area became infested with ants – I mean totally infested , so I wouldn’t recommend it.
Cornmeal is damaging to the digestive system of worms, yet cutworms will eat it till they drop dead.
Try sprinkling some in the affected areas of your garden. But don’t get carried away as it draws rodents and other insects. If it doesn’t draw other pests it eventually grows fungi which can also be damaging.
Sprays/Pesticides must be applied in the pre bloom stage to prevent injury. Pesticides such as Pyrethins
Proper sanitary practices are vital to the health of your garden. Proper sanitation can help to ensure disease-free pest-free and productive gardens. Try to keep the garden free of any diseased dead or damaged plant materials.
Remove cuttings from pruning and trimming and either destroy them – if diseased, or send them to the compost pile. Leaving rotting fruits and vegetables in the garden is like a written invitation to unwanted pests and diseases.
If a diseased or dead plant part has to be cut, the microorganism that caused the problem is probably on the tool you just used. Like a surgeon, sterilize all tools by washing in soap and water – rubbing alcohol wouldn’t hurt either.
If you pinch off diseased plant parts, wash hands before handling any other plants.
Keep Weeds under control. Till the soil in the spring before planting to expose and kill larvae that wintered over in the soil.
Diverse gardens that include a symbiotic mingling of flowers and vegetables are a poor environment for insect pests as they also attract many natural predators, lacewings and ladybugs in particular. Praying mantis will prey on the moths.
Adult moths can be trapped with light traps by night. Beneficial Nematodes are useful against cutworms as they hide under the soil surface during the egg and larva stages.
Related: Control Leafroller Caterpillars