Cutworms and Cannabis: How to Detect, Prevent, and Eliminate These Destructive Pests

Growing cannabis comes with its fair share of challenges, and one such challenge is cutworms. They are one of the worst pests you can encounter. These tiny caterpillars may look harmless, but they have a bad habit of wrecking seedlings overnight. 

If you’ve ever woken up to find your young cannabis plants mysteriously chopped at the base, you might have these little troublemakers lurking in your soil. Learn all about these pests in this article below. 

What Are Cutworms?

Despite the name, cutworms aren’t actually worms — they’re caterpillars, the larvae of various moth species. And unlike the pretty moths you might see fluttering around your garden, the ones responsible for cutworms aren’t winning any beauty contests.

Cutworms are infamous for attacking seedlings, often mistaking them for grass. They go straight for the base of the stem, chewing through it until the plant is completely severed — hence the name “cutworm.”

 It’s not that they have a personal vendetta against cannabis, but if your plants are in their path, they won’t hesitate to feast.

These pests typically emerge at the start of the growing season after spending time hiding in the soil. If you don’t catch them early, they can devastate your young plants before they even have a chance to thrive. 

A single cutworm can take down a seedling in just one night, making them a serious threat to any grower.

Cutworms range from 1 to 2 inches in length and are usually brown or gray with a slimy texture. However, some species come in different shades and may have spots or stripes. The two most common types you’ll likely run into are:

• Black cutworms (Agrotis ipsilon)

These are the most common and can be identified by the dark spots along their bodies. Once they mature, they turn into dark sword-grass moths.

• Variegated cutworms (Peridroma saucia)

These have a mottled brown appearance with a faint white stripe running down their backs.

If you ever disturb a cutworm, you’ll notice that it curls up into a tight ‘C’ shape as a defense mechanism — kind of like it’s pretending to be invisible.

Lifecycle of Cutworms

Cutworms undergo complete metamorphosis, which is comprised of 4 stages, namely egg, larva (caterpillar), pupa, and adult moth. 

Although it's not mandatory, it might help you to understand a bit about their lifecycle for early detection, prevention, and control to save cannabis plants from a great deal of damage.

1. Egg Stage

The life cycle of a cutworm starts when the adult moths come and deposit eggs on soil, atop plant stems, or on surrounding plants. The eggs are tiny, round, and usually white, cream, or pale yellow, so they are hard to spot.

Typically, the eggs are laid in groups or clusters on loose soil, plant debris, weeds, and lower stems of cannabis plants. However, you may find single eggs, too. Female moths prefer to lay eggs in weedy, unkempt areas as they have moist soil and dense vegetation. Most types of adult cutworms lay eggs in late summer or early fall. However, some overwinter as eggs and hatch in early spring when temperatures rise.

2. Egg Development & Hatching

Depending on temperature conditions, they could hatch within 3-7 days or take up to two weeks for hatching due to cool temperatures.

The eggs hatch quicker when the temperatures are warmer and moisture levels are high, but the opposite is true as well since cold or dry conditions will cause a delay. The instant they hatch, the larvae will start eating cannabis seedlings or other tender plants.

How to Disrupt the Egg Stage

• Tilling soil during fall and early spring brings eggs to the surface, where they die.
• Destroy plant debris and weeds to reduce egg sites.
• You can prevent the eggs from hatching by applying diatomaceous earth and neem oil (more on this below).

To help with egg control, encourage natural predators, including ground beetles, ants, and parasitic wasps.

3. Larval (Damaging) Stage

The larval form of a cutworm is the most damaging stage. Once they hatch, the larvae start feeding right away and become bigger and more damaging. This stage lasts three to five weeks, depending on the climatic conditions.

Characteristics of Cutworm Larvae

The larvae may appear in different colours like green, brown, grey, and even black with stripes or spots. When bothered, they curl up tightly into a "C" shape as a soft-bodied caterpillar. Fully grown larvae can be as big as 5 cm long, but the smaller larvae measure only a few millimeters in size. 

They are not easy to spot because they feed at night and not in the day. During the day, cutworms hide in the soil, in plant debris, or at the base of cannabis plants. They only come out at night to feed.

4. Pupation and Adult Moth Stage

When the larvae reach their full size, they stop feeding and burrow deeper into the soil (1 to 4 inches) to pupate. Most often, this happens in two or three weeks, or faster in warm weather.

Here's how you can identify the pupa:

• Dark brown cutworm pupae are smooth and cylindrical in shape.
• They pupate underground to escape their enemies and the weather.
• Some types overwinter as pupae and emerge as moths in spring.

5. Adult Moth Stage

The mature cutworm moths emerge from the pupae, mate, and start the cycle again by laying eggs. These moths of 1 to 2 inches in wingspan are medium-sized and mostly dull, brown, gray, or tan. In addition, they fly at night and are strongly attracted to lights. Although adult moths are harmless to cannabis plants, they are vital for reproduction and spreading infestation.

How to Interrupt the Pupation and Adult Moth Stage

• Before planting, till the soil to disrupt pupae with the emergence of moths.
• Getting predators that already live in the soil will help reduce pupal survival.
• You can use some traps made from pheromones to catch adult moths.
• By reducing outdoor light usage, you can prevent the moths from getting attracted to them. 

How to Spot a Cutworm Infestation?

Cutworms are thieves in the night, hard at work while you are sleeping and causing harm to your plants before you even notice. Yet, their damage leaves plenty of clues that let you spot cutworm damage and deal with the pest.

1. Seedlings Cut at the Base

When a young cannabis seedling is cut at the base and left wilting or completely removed from the soil, it can be one of the clearest signs. Cutworms don’t nibble on leaves like other pests that sap the strength of the plant. They eat the stem of the plant overnight, and it dies. If the seedlings of cannabis are lying on the ground lifeless, cutworms are most definitely the culprits. Few pests cause this kind of destruction, which is why cutworms are such a major headache — they don’t just damage plants, they straight-up eliminate them.

2. Nocturnal Activity – Nighttime Inspection

Because cutworms feed at night and stay hidden during the day, catching them is next to impossible. They prefer to do their damage under the cover of darkness. Check the base of your plants and the surrounding soil carefully — cutworms blend in well with dirt, so you’ll need a sharp eye to spot them.

Thus, take a walk in your garden at night with a flashlight and check your plant bases for confirmation. These caterpillars usually attach themselves to the lower stem or burrow slightly into the ground, which camouflages them with dirt or plant bits.

3. Disturbing the Soil to Reveal Hidden Larvae

If you think you have cutworms but haven’t seen any, try gently disturbing the surface of the soil around your plants. Cutworms curl up in the soil during the day, so disturbing the top layer of soil can reveal them and let you remove them. If you find big and curly caterpillars hiding near the base of the plant, you’ve found them.

4. Wilting or Leaning Young Plants.

Although cutworms don’t only damage seedlings, they do damage slightly older cannabis plants. If a young plant suddenly wilts, leans, or appears to struggle, inspect the stem near the soil line. If the plant looks like it was partially chewed or weak, then the cutworms have started munching on it, but they haven’t completely cut it off yet.

5. Chewed Leaves and Random Holes

Cutworms are called cutworms because they cut through the stems of plants or crops. However, the cutworms also feed on leaves. If you see odd holes in cannabis leaves or broken edges, especially around the base, the culprits could be cutworms and/or similar caterpillars. It occurs more often with older larvae that have become too big to camouflage in the dirt and are now eating higher up on the plant.

6. Sawdust-Like Frass (Droppings) Near Plant Bases

You can identify cutworm activity by spotting their small, brownish-black droppings near plant bases or on the soil. You may find cutworm frass on leaves and on dirt near your plant’s base. This frass looks like little bits of sawdust, which indicates that they have been busy munching. Examine the area near the leaves early in the morning for frass to know whether the larvae are present.

7. Missing or Severely Damaged Transplants

If you recently transplanted cannabis seedlings and they go missing overnight, cutworms might be the cause. They are often eating the young plants and dragging them into the dirt, making it look like the seedlings have completely disappeared. Sometimes, seedlings may not be pulled underground, but they will be infested with deep feeding grooves on the stems.

8. Uneven Stem Damage and Partial Girdling

Even if cutworms do not sever stems completely, they may chew through them. Stems with uneven bite marks, small gouges, or half-eaten stems with cutworms may still mean that cutworms are present in the area. While a damaged plant may not yet be falling over, it may not be taking up water and nutrients as it should. Therefore, it may be growing slowly or wilting at a slower rate than expected.

9. Birds and Predatory Insects Digging in the Soil

Birds scratching at the soil around your plants means that you probably have a cutworm infestation. Some birds, such as robins and blackbirds, eat cutworms. You can also see ground beetles and beneficial wasps hunting in places where cutworms are taking over your garden.

10. Sudden Plant Death in Patches

Many pests are guilty of killing the plant gradually, whereas cutworms will do it overnight but only in patches. If you wake up to a patch of dead or damaged seedlings, it means cutworms are present. These pests usually remain in one place until their food runs out, so if you see concentrated damage, check the soil closely.

Keep an eye out for other signs to catch them early so that you can manage them before they destroy your cannabis.

How to Get Rid of Cutworms in Your Cannabis Garden?

Dealing with cutworms isn’t as hard as it seems. In fact, with just a little effort, you can get rid of these pests in no time. You won’t need fancy equipment or a degree in entomology — just a flashlight, some patience, and maybe a strong stomach. 

Here’s how you can evict these freeloaders from your cannabis plants.

• Pick Them Off by Hand

It might not be the most glamorous method, but the easiest way to remove cutworms is by hand. Luckily, these pests don’t bite, sting, or move particularly fast, so all you have to do is find them and pluck them off.

Of course, touching slimy caterpillars isn’t everyone’s idea of a good time. If you’re squeamish, just throw on a pair of gloves and grab a flashlight. 

Since cutworms are nocturnal, the best time to hunt them down is after dark. Once you spot them, toss them into a container of soapy water — that’ll take care of them for good.

• Use Cornmeal or Diatomaceous Earth

If you’d rather not spend your evenings digging around in the dirt, you can go for a hands-off approach. Sprinkling cornmeal or diatomaceous earth around your plants can help eliminate cutworms without you having to touch a single one.

Cornmeal might seem like an odd choice, but cutworms love the stuff. The problem? Their digestive systems can’t handle it. Once they eat it, they swell up and die — game over.

Diatomaceous earth, on the other hand, works differently. It’s a fine, powdery substance made from fossilized algae, and while it’s completely harmless to humans, it’s a nightmare for insects. 

On a microscopic level, it’s like shattered glass — when cutworms crawl over it, it slices through their exoskeletons, causing them to dehydrate and die. Brutal but effective.

Coffee grounds and eggshells work similarly. Cutworms avoid crawling over rough textures. So spread eggshells, coffee grounds, or wood ash at the base of the plants to deter them. Plus, they provide nutrients to the soil as they break down, meaning it’s a great way to kill two birds with one stone. 

• Try Chemical Insecticides

If you’re dealing with a serious infestation and need a stronger solution, chemical insecticides might be the way to go. Products like Bug Blaster are designed to wipe out all sorts of garden pests, including cutworms.

Just make sure to pick an insecticide that’s safe for cannabis. Some pesticides contain chemicals that could harm your plants or leave unwanted residues. Always read the label, follow the instructions carefully, and avoid overusing them — especially if you want to keep things as natural as possible.

Recommended Insecticides for Cutworm Control

Severe cutworm infestation may need insecticide application. But we must just go for effective and safer products that will not leave pesticide residue on the consumable parts of cannabis. Here are the top insecticides for cutworms, along with their usage and precautions.

• Spinosad – Natural bacterium insecticide (organic-compliant)

Spinosad comes from a soil bacteria called Saccharopolyspora spinosa and is considered very safe for organic cannabis growers. This insecticide is specifically for cutworms but won’t affect ladybugs or beneficial beetles. Spinosad works against the nervous systems of cutworms, causing paralysis and death after one to two days. 

You should apply this in the evening or early morning when cutworms are active; focus on the soil and the base of plants, not the leaves or buds. If cutworms persist, reapplication may be needed every 7-10 days. Since it breaks down quickly in the sun, using it at night will be more effective.

• Pyrethrin-Based Insecticides – Fast-Acting Contact Killers

Cutworms are very effectively controlled by these plant extracts of pyrethrins, which are neurotoxins. It kills them on contact by paralyzing them immediately. However, pyrethrins are not very persistent in soil, so it is best to use them for active infestations. These insecticides should be applied only at night as they can harm bees and other beneficial insects. Don't spray directly on flowering cannabis plants, as the residue of pyrethrins can affect the final product.

• Permethrin

Permethrin is a synthetic version of pyrethrin that provides extended protection but has a higher environmental impact. It disrupts the nervous system of cutworms and can persist in the soil for several weeks, making it a highly effective but last-resort option. However, it’s not very environmentally friendly. 

Keep in mind that although permethrin is very effective and powerful, it can harm other beneficial organisms. You will have to avoid it completely if you’re growing organically. Still, use it when you have no other options and if the infesttauon is severe even if you’re not growing organically. 

Moreover, growers must avoid applying permethrin within 14 days of harvest to prevent cannabis flowers from being contaminated. Unlike natural pyrethrins, permethrin’s residue can linger around and affect soil health. 

So, when choosing insecticides or pesticides for cutworms, it’s best to choose one that is safe, like Spinosad, before trying something stronger. Proper timing, recommended frequencies, and targeted application with the necessary precautions can help keep the cannabis plant healthy and safe for use.

Some growers prefer to skip chemical solutions altogether, but if you choose the right product, it won’t hurt your plants. The choice is yours.

Safe Timing & Application of Insecticides for Cutworm Control

Remember that you're going to be consuming cannabis in some way, whether you're smoking or eating edibles. So, it's even more important to use insecticides responsibly so as to not leave harmful residues and harm beneficial insects in the grow.

When to Use Insecticides on Cannabis

If you're wondering when it's best to use insecticides, here are a few tips: 

• If the damage caused by cutworms on the plants is more than 25%, their infestation is severe. 

If more than a quarter of your plants have shown cutworm damage, you’d definitely want to take action. Such damages indicate cut stems, missing leaves, or dead seedlings.

If organic methods have not worked, you can use insecticides in the early vegetative stage when cutworms are most likely to attack seedlings and young cannabis plants. If many seedlings are being destroyed overnight, insecticides might prevent the total loss of yields.

Keep in mind not to use insecticides that will harm the pollinators as well as the beneficial predators in your garden.

How to Apply Insecticides Safely

There are some best practices for applying insecticides to cannabis that will reduce the risks and increase effectiveness. Here they are: 

• It is better to apply the insecticides in the evening or early morning as cutworms are more active during the night. So, nighttime treatments will be more effective when applied during their feeding time.
• For 7 days, apply the insecticide on the evening of the first day and in the morning of the seventh day. Cutworms are most active during peak feeding hours. Don't spray on cannabis buds or leaves, as insecticide residue can cling to the useful parts.
• Ensure that you read the label of the product carefully and do not apply in excess.
• If you apply insecticides close to the harvest period, then the cannabis that you collect might contain chemicals that are toxic for endogenous and/or animal consumption. Hence, it is best not to apply this substance to your plant before you harvest it. 
• One good idea is to switch out insecticides in order to ensure the pests don't get resistant to them. If you are using multiple applications, switch between insecticides with different active ingredients, like Spinosad, so that cutworms don't develop resistance to one of them. 

Always wear gloves, long sleeves, and a mask when applying insecticides to avoid inhaling the pesticide or getting it on your skin. 

• Use Biological Warfare

For a more eco-friendly approach, you can fight fire with fire — well, bacteria, in this case. Bacillus thuringiensis (BT) is a naturally occurring soil bacterium that produces toxins lethal to cutworms and other caterpillars but does not harm cannabis plants, beneficial insects, or humans.

It’s one of the most recommended biological control methods, even by agricultural experts. When larvae eat Bt, it disrupts their digestion and causes them to stop eating before they die a few days later, but it can still be effective against older ones. Just follow the instructions on the packaging, and if possible, hold off on watering your soil for a day or two after applying it — unless the manufacturer suggests otherwise.

To use Bt, apply a Bt spray onto cannabis plants at night when larvae are feeding. Then, reapply after heavy rain or watering.

• Recruit Some Natural Predators

Want a hands-free security system for your cannabis plants? Consider enlisting nature’s pest control team.

Certain beneficial insects — like parasitic wasps, spiders, and beetles — love feasting on cutworms. Even frogs can help patrol your garden, keeping these pests in check. You can find beneficial insects at gardening supply stores, and once they’re introduced to your grow space, they’ll get straight to work hunting down any unwanted guests.

Natural Predators of Cutworms

Many insects, birds, and other organisms eat cutworms at various life stages. These predators are important to our environment. So, you simply need to create conditions that will encourage them to find their natural enemies, which is an effective means of reducing infestations.

• Ground Beetles (Carabidae family)

Ground beetles are useful insects that hunt and eat cutworm larvae. They mostly hunt cutworms at night while these worms are active. They can be an excellent way to keep your plants safe from cutworm infestation. To attract them, avoid excessive tilling, which destroys their habitat. In addition, plant clover, alfalfa, or cover crops to provide shelter.

• Parasitic Wasps (Trichogramma and Cotesia species)

Cotesia wasps are really good at killing cutworm caterpillars. Their larvae grow inside the caterpillar and eat it. To attract them, plant yarrow, dill, and fennel, which produce nectar. Also, don't use broad-spectrum insecticides that would kill your beneficial wasps.

• Tachinid Flies (Tachinidae family)

These flies deposit their eggs on or close to cutworm larvae. When the eggs hatch, the larvae burrow into the cutworm and kill it from the inside out. To attract them, grow nectar-producing plants such as parsley, sweet alyssum, and coriander. 

• Birds 

Birds like Robins, Wrens, and Sparrows eat cutworms, moths, and other caterpillars that help keep their population under check before they turn nasty. To attract them, install birdhouses and perches, and avoid using harmful pesticides that can poison birds.

• Nematodes (Steinernema and Heterorhabditis species)

Microscopic roundworms known as beneficial nematodes kill and consume cutworm larvae in the ground. These nematodes invade the cutworm's body and discharge bacteria that can kill the pest in 24-48 hours.

To apply them, purchase nematodes from garden suppliers. Mix it with water and apply to moist soil in the evening or early morning.

• Neem Oil – A Natural Repellent

Neem oil is a natural insecticide that disrupts the growth and feeding of insects. It affects cutworm eggs and larvae without harming helpful insects. To use it, first make a neem oil and water solution and spray it on the soil, stems, as well as leaves. Apply weekly as a preventative measure.

• Crop Rotation – Breaking the Lifecycle

Rotating cannabis with non-host crops (such as garlic, onions, or marigolds) disrupts the cutworm lifecycle. This method prevents larvae from finding food and forces them to move elsewhere.

How to Prevent Cutworms from Coming Back?

You’ve kicked cutworms out of your garden — great! But if you don’t take preventive measures, they’ll be back like uninvited party crashers. Here’s how you should make sure they don’t return.

• Inspect Your Garden Regularly

Regular inspections are your first line of defense. Since cutworms are nocturnal, check your plants at night, dawn, or dusk when they’re most active. A quick shuffle of the soil around your plants can also help you spot any lingering pests before they get a chance to multiply.

• Keep Grass and Weeds Away

Cutworms love grass, and moths prefer laying their eggs in weeds. If you keep your garden weed-free and your plants clear of overgrown grass, you significantly reduce the risk of cutworms sneaking back in.

• Plant Sunflowers as a Decoy

Sunflowers act as a natural cutworm trap. If you plant them around the edges of your garden, cutworms will go for the sunflowers first, leaving your cannabis plants alone. Once you see cutworms hanging around the sunflowers, simply remove them with soapy water.

Bonus: Sunflowers also add a nice aesthetic touch to your garden!

• Create a Cutworm Barrier

If you want to prevent cutworms from reaching your plants, set up a physical barrier around the stems. You can use toilet paper rolls, small PVC pipes, and aluminum foil. 

Just push the roll or pipe about an inch into the soil around the plant’s stem. This stops cutworms from crawling up and chewing through your plants. If you use aluminum foil, be sure to check it regularly to ensure it stays intact.

Outdoor and Indoor Grows Cutworm Management

Due to environmental factors, cutworm prevention differs for outdoor versus indoor cultivation.  However, outdoor cannabis plants are more vulnerable to cutworm attacks due to exposure to moths, eggs, and larvae in the soil.

Best Strategies for Outdoor Grows

• To reveal and eliminate overwintering larvae, till the soil in early spring.
• Put stem collars on young plants to prevent larvae from cutting the stems.
• Using helpful nematodes to kill cutworms before they hatch.
• Use insecticides like Bt or Spinosad by spraying the base of the plants in the evening when the larvae are feeding on the plants.
• Picking off cutworms at night if needed.
• Try planting marigolds, basil, or onions with your plants. They will repel moths and laying eggs.

Best Strategies for Indoor Grows

Indoor cannabis grows are less susceptible to cutworms but can still face infestations if contaminated soil, plants, or moths enter the space.

• Check and sanitize your soil before taking it indoors to eliminate hidden larvae.
• To prevent a cutworm infestation, use sticky traps and insect screens at the entrance to your grow rooms.
• Before adding them to your indoor grow room, make sure to quarantine new plants. 
• If seeds have been detected, apply this to the plant and the soil.
• Keep your grow space clean of plant debris and vacuum the area consistently to prevent pest establishment.

Summary: Cutworms and Cannabis: How to Detect, Prevent, and Eliminate These Destructive Pests

Cutworms might be small, but they can cause big problems for your cannabis plants. The good news? With the right approach, you can eliminate them and keep them from coming back. 

Whether you go for hands-on removal, natural deterrents, or chemical solutions, staying proactive is the key to protecting your garden. Keep an eye on your plants, maintain a clean grow space, and use preventive measures to ensure these pests don’t make a comeback. A little effort now will save you a lot of frustration later.