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Pest Guide – Cutworms

Pest Guide: Cutworms

Every gardener needs to deal with damaging pests, and marijuana growers are no exception. Cannabis is susceptible to many dangers, but cutworms are some of the most common and destructive pests that affect young plants. As a result, growers must understand how to prevent and eliminate them when necessary. Indoor cultivation is the only way to guarantee the insects will not infect your crops so you are planting outdoors, there is a good chance you will need to deal with cutworms. The best way to protect plants is to learn everything you can about the insects. Become an expert at identifying cutworms and using preventative measures that keep them away. Successful growers will also need to learn everything possible about how to eliminate them if they do appear.

What Are Cutworms?

In order to keep your crops safe from cutworms, you need to recognize and understand them. Cutworms are the larvae of various nocturnal moths. They live in high grass, debris piles, and the soil. Eggs hatch in the fall and are left in the same types of shrouded locations. Larvae are night feeders and eat the first part of any plant they encounter. That is generally the stem. The insects are most destructive just after they emerge from hibernation, which is usually at the beginning of the growing season. It is easy to mistake them for grubs, but they are actually caterpillars.

Recognizing Cutworms

The first step in protecting your crop is to learn how to recognize cutworms. Different species can be various colors. They are about two inches long and are often curled up and not moving. If you touch one, they will automatically curl up. Worms are generally grey, pink, or green and black.

Black worms have dark spots and grow into dark sword-grass moths. There are also mottled brown species known as variegated cutworms. Adults are moths with wings that are about 1 ½ inch long. It is essential to keep an eye out for adults because females will lay eggs in the soil.

Understanding the damage that cutworms cause

While it is vital to protect plans from all damage, cutworms pose an especially lethal threat. According to professionals writing for Growing Organic, the insects get their name from the way they feed. Because they eat the beginning of the plant’s stem, worms cut the plants down. Even if you do not spot worms right away, you will know they are present if you see the tops of plants lying on the ground.

The larvae consume roots and bottom foliage of young plants and kill them from under the soil. An infestation can destroy a crop of seedlings in a single night.

Signs of Cutworms

Since there are several types of insects that can threaten cannabis crops, it is vital to ensure you are dealing with cutworms before taking action to protect the plants. The most important thing is to identify the damage as early as possible.

Check plants in the morning to identify easy-to-see, fresh destruction.  Look for plants that seem to be cut off near the ground or appear to be wilting. The worms cause wilting when they chew on stems without severing the plant entirely. During the summer, they can crawl to the tops of plants and damage them there. Also, search for the droppings that cutworms leave when feeding.

Examine your crop in the late afternoon and evening to spot active cutworms.  Run a hand over the soil and roll over the soil clumps within a foot of plants. These are familiar hiding places for cutworms. If they are present, they will curl up and look like the letter “c” when disturbed.

Preventing Cutworms

It is easier to keep destructive insects away than to get rid of them once they have infested your crop. Fortunately, you can utilize a variety of professional methods designed to keep cutworms from reaching young plants.

Use a Grow Tent to Isolate Seedlings

The most straightforward way to keep insects away from crops is to create a protected environment, even if you are cultivating plants outdoors. You can find portable, reusable grow tents that act like greenhouses. Since you are cultivating crops hydroponically and with grow lights, they are safe from environmental threats.

Keep Surrounding Grounds Neat

When your crop is exposed to the environment, it is essential to keep the surrounding area as neat and trim as possible. Mow the grass and clear away debris. In that process, you will remove some worms that are hiding. It also eliminates the tall grass where females like to lay eggs.


Use compost rather than green manure that could encourage moths to lay eggs.

Make Plant Collars

You can create basic DIY collars that protect plants. Paper towel and toilet paper rolls are ideal. You could also use PVC, metal cans, or paper cups. Cut them into two or three-inch rings and then make slits in the sides so they can wrap around plants. Gardening experts at Mother Earth News recommend pressing collars an inch into the soil. Worms cannot crawl under these barriers.

Use Kitchen Ingredients

Save eggshells and coffee grounds and then bury them around plants to repel worms, which do not like the scents.

Delay Planting

If you put off planting cannabis until later in the season, you eliminate the cutworm’s food supply.

Cultivate the Earth

Till the soil late in the season to expose and kill eggs that females have laid. You also destroy the weeds that are the cutworm’s natural habitat.

Create a border of companion plants

Some growers circle gardens with sunflowers that attract cutworms. Insects feast on the border plants instead of cannabis, and sunflowers repel some pests. You can plant tansy near a crop to repel cutworms as well as other destructive insects.

Using Beneficial Nematodes to Protect Cannabis

Both indoor and outdoor marijuana growers can benefit from adding nematodes to soil. Nematodes are microscopic roundworms that emit insect-killing bacteria. Cutworms eat the tiny roundworms, which then release toxins that kill the insects. Nematodes use larvae tissue as food.

There are harmful and beneficial nematodes. Like professional organic cannabis growers, you can buy helpful species from distributors. The nematodes are added to a liquid that you spray onto the soil every few weeks.

Microscopic nematodes are often combined with other organisms and added to soil to protect plants from a variety of insects, including cutworms. That allows growers to avoid using chemicals that could be toxic when cannabis is smoked.

Benefits of applying beneficial nematodes:

  • They interrupt worm’s lifecycle to limit damage.
  • They are compatible with many fertilizers and organic insecticides.
  • They remain in the soil to provide continued biological pest management after initial application.
  • They leave a residue, which ensures a clean product upon harvest.

How to Stop a Cutworm Infestation

If you see signs of cutworms on your plants, you can save the remaining crops by using preventative measures, but you must remove any existing insects. The best way to keep cannabis safe is to employ a combination of prevention and elimination methods, and, as always, you need to be vigilant to prevent the problem from returning.

  • Remove Worms by Hand: The most difficult but least expensive way to remove worms is by hand. Make sure you have cleared and trimmed the area around your garden first. You will need to go out at night when cutworms are active. Use a flashlight to find them. Pick worms off and drop them into soapy water, which destroys them. Repeat the process every few nights until there are no signs of the insects remaining.
  • Use an Organic Pesticide: An organic pesticide like bacillus thuringiensis will kill cutworms. The best time to apply a pesticide is late in the afternoon, close to dusk. You should be aware that the pesticide will also kill butterflies. Since butterflies are essential to pollination, you might want to consider an organic alternative
  • Apply Diatomaceous Earth: You can sprinkle the area around stems with diatomaceous earth. It’s a natural powder made from ground-up fossils. The powder kills insects that come in contact with it.
  • Mulch to Draw Frogs: Mulch is a loose, fertile soil composed of decayed plant matter. It is the same material you would find underfoot in a forest and contains many living things, including insects that attract frogs. When you add a layer of mulch around your marijuana plants, it attracts frogs and parasitic wasps that will make a meal of cutworms and other pests.
  • Encourage a Variety of Natural Predators: When you are planning your garden, design it to attract insects and animals that are cutworm predators. For example, create a bird or firefly-friendly environment. Skunks also love to dig up cutworms, so if you spot a skunk near your crop, let it be. Place bird feeders and baths near plants. Birds will naturally find and snack on larvae.

Closing Thoughts

Pest control is key to producing a healthy cannabis harvest. Young plants are especially susceptible to cutworms that can quickly destroy a crop, so growers need to be able to identify, prevent, and eliminate the insects. Fortunately, anyone can solve the problem by using tips from professional growers. Experts provide dozens of ways to avoid infestations and save crops once cutworms appear. Apply these methods to your crops and watch your harvest flourish!