How to Identify and Control Cutworm Damage in Your Backyard Garden

Cutworms are an interesting pest that you don't normally know you have until a favorite plant simply keels over - during the middle of the night.

The adult is a brown moth and she lays her eggs on grass tips or on the soil next to stems in the fall. In the spring, the egg hatches and a larva emerges and begins developing. As it develops through 6 stages, it likes to eat green growing matter.

Some of the larvae will climb up and chew on leaves while others gnaw away at the soft stems of young plants. After they eat enough of your plants, they mature, pupate in the ground, and emerge as moths to begin laying eggs.

Cutworm Larva

The larva stage you're interested in that does all the damage is a small caterpillar - one to two inches long - with a grey or brownish-gray body with white stripes down the sides. It is a plump little fellow and hairless. When this caterpillar is disturbed, it curls up into a ball.

You'll get lots of advice on some organic pages about scouting for problems, seeing if there is any damage and handpicking the caterpillars to drown or squash them. (These techniques work well.)

Cutworm - image courtesy Wikimedia

Proactive Controls

I'm a great believer in proactive control.

The eggs are laid in the fall next to weeds so get rid of the weeds.

They lay eggs in turf, so get rid of turf close to your vegetable gardens. (have a perennial flower border surround your garden)

But the most useful trick is to simply put a collar of stiff paperboard around your plants when you plant them. The collar should stick up on top of the soil a few inches and go below the soil an inch or more. This light cardboard (the stuff drink boxes are made of) will disintegrate in the soil but will protect the plant until it is too large for the caterpillar to eat.

You can use diatomaceous earth around the base of the plant and as the worm travels over/through this substance, it will be cut up and dehydrate.

I'm told you can surround your plants with a collar of molasses and this sticky substance will also deter this pest.

Some gardeners say that crushed eggshells will do the same thing as diatomaceous earth. This has not been the case in my garden with slugs (often recommended for slugs) and I'm not sure it will be the work with cutworms either as the eggshells aren't really that sharp (particularly when compared to diatomaceous earth)

Some garden authors recommend dusting the base of the transplant with wood ash.

Encourage Birds

Encourage birds. Bluejays, sparrows, blackbirds and wrens feed on cutworms.

Skunks also dig and feed on cutworms but I'm not so sure you want to encourage them. :-)

Beneficial nematodes also eat cutworms and these can be found at better garden shops. Note they are dynamite at controlling lawn grubs as well.

Some parasitic wasps lay their eggs in the body of the cutworm but again, I tell you this for your information rather than action.

But for my money, cutworms are most easily controlled by putting a collar around the stem of transplants when you put them in the garden. No fuss - no muss. Some folks use cardboard or heavy paper. Some have recommended aluminum foil. I prefer a heavy paper as this gets the transplant up to a size the worms won't bother them and is easier to wrap around the stem.

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