How to Protect Your Garden from Cutworms

Cutworms can destroy a vegetable garden overnight!

And unfortunately, it happens way too often! You have just finished planting your garden and transplanted your seedlings that you have been pampering indoors for weeks, you are going to sleep but when you go to the garden the next morning this nightmare is waiting for you: plants cut clean through at the base! The culprit, the famous cutworm. Let's talk about how to recognize them, prevent them and get rid!

What are cutworms?

Cutworms are the larvae of several species of moths. Moths lay their eggs on plant debris from spring to fall. The larvae can therefore hatch at any time during this period, but usually the fall ones will overwinter to be "ready to attack" early in the spring when the seeds and small plants are vulnerable. It is therefore at the beginning of the gardening season that they cause the greatest damage.


How can I recognize them?

Cutworms are sneaky and usually hide during the day. To find them, you have to go to the garden at dusk, on a cloudy day or with a flashlight in the evening when it is dark and look at the base of your young plants or seedlings.

Different species can be different colours. Obviously they can be gray, but also pink, green or black and be as long as 5cm (2 in). When they are not moving, they are generally rolled up on themselves.

When they become adults, the cutworms evolve into moths with brown or dark gray wings (see photo). They are about 4cm long and their wings also spread out to about 4cm. Recognizing the adults will keep you alert as the female will likely lay her eggs in the dry soil of your garden.

cutworm beside damaged plant

How can I tell if a plant has been damaged by a cutworm?

In the spring, they gnaw the stems of small plants at the base or even below ground level. They also feed on the roots and leaves of these plants. Usually, even if only the bottom of the plant is affected, the entire plant will wilt and die. They cause a lot of damage in gardens, and very quickly.

In the summer, they may also climb to the top of plants to feed on young leaves.

How can I prevent cutworms?

In order to avoid the worst, we suggest you try these few tips:

  • Protect each plant stem by wrapping a cardboard or aluminum foil collar at least 4" high around it.
  • If you see a cut stalk near the ground, poke your finger around it 1-2 inches deep and you'll likely find the culprit.
  • Go hunting for cutworms. A few times a week, go out with a flashlight, gloves and a bucket filled with soapy water when it gets dark. Pick up the cutworms and put them in soapy water.
  • Sprinkle diatomaceous earth around the stems of the plants you want to protect. This natural powder will dehydrate the worms. Be careful, it acts in the same way with beneficial insects in the garden such as bees or butterflies, so it is very important not to use it near flowers.
  • Apply a biological insecticide at the end of the afternoon like this BTK one, which is in fact a bacterium which attacks soft-bodied insects and their larvae.

How can I get rid of them for good?

  • Avoiding planting out seedlings too soon will cut off their food source, and prevent much damage. 
  • To keep laying mothers away, avoid keeping long grasses around your garden. Continue to mow around your garden in the fall to expose dormant eggs or larvae hidden in these plants or on the soil surface.
  • Birds are a natural predator of cutworms. Consider creating an inviting environment for them to come and enjoy them.

Good luck and happy harvesting!

Photo credits: and John Obermeyer, Purdue University.