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caterpillars during flowering

Cannabis Caterpillars and How to Get Rid of Them on Weed Plants

Spotting caterpillars during flowering is like seeing Jason Voorhees appear at the lake while you’re swimming. They’re somewhat squishy and cute, but these insects are also crazed munchers that can harm your cannabis plants.

Do you grow marijuana crops? If so, we’re about to share essential information to help you deal with caterpillars. Discover the signs of an infestation and learn how to prevent these chunky critters from attacking your greenery.

caterpillars eggs
Caterpillars leave eggs on the bottom side of the leaves

What are caterpillars, and what do they look like?

Caterpillars are insects in the larva stage. They eventually develop into adult Lepidoptera, commonly known as butterflies and moths. Caterpillars on weed plants are typically only a concern for those engaged in outdoor cannabis growing.

Here are some defining features to help you spot them: 

  • Six legs
  • Five stumpy prolegs with hooks that make it easier to grip onto things
  • A tube-like body made of small round segments, crucial for separating caterpillars from worms
  • A small, short head
  • An expandable thorax
  • A long abdomen
cannabis caterpillars
Which caterpillars you can find on cannabis plants

There are many species, all with varying physical attributes. Here are some common types of cannabis caterpillars and their distinct features: 

  • Painted lady: The appearance of these caterpillars changes with each instar. In the early stages, they look like light gray worms with bulbous heads. As they grow, they develop prominent spines and darker bodies with unique orange and white markings.
  • Saltmarsh caterpillar: This species has a diverse color palette ranging from reddish brown to pale yellow. The darker ones sometimes have orange-red markings. They’re covered in setae or tufted hairs.
  • Yellow woollybear: These caterpillars have a pale yellow to light brown shade. They’re covered in lots of setae and look like yellow fluff balls. They also have one uniform color, while other species tend to have a blend of hues.
  • Zebra caterpillar: Living up to their name, these caterpillars have black and white markings with yellow stripes. They also have a red head and thorax. The yellow lines are striking and distinct, making them easy to spot.
  • Variegated cutworm: These insects are typically brown, but body colors vary. The most distinguishable feature is the handful of light yellow circular dots running along their spine.

While other caterpillars may be picky about the type of food they prefer, like fan leaves or stems, variegated cutworms don’t have a preference. They eat buds, shoots, and mature foliage, posing a threat from the cannabis seedling stage to harvest. 

Caterpillar damage on marijuana plants

caterpillars damage on cannabis
Holes in cannabis leaves caused by caterpillars

Identifying the different species is essential, so if you spot caterpillars in buds, you’ll know their strategy. Zebra caterpillars are typically the most frequent problem with cannabis plants. They graze on the fan leaves, chewing away at the tender tissue.

a bud damaged by caterpillars
A big hole in a cannabis bud made by caterpillars to get in there

It’s rare to see other species of caterpillar on marijuana plants, but if you spot them, act fast. They’re more likely to damage the essential anatomy like stems and colas. Once the major structural parts are impaired, your flora may never recover.

brown and dead bud caused by caterpillars
Brown and dead bud growing tips caused by caterpillars

By causing structural damage, they render your flora unprotected by the elements. This damage has a ripple effect that makes your plants susceptible to mold and other diseases. When growing outdoor weed seeds, pay careful attention to nearby insects.

Signs of a caterpillar infestation

With caterpillars, the damage ranges from a few bite marks on your leaves to large holes in the main cola. Here are some critical signs that these hungry critters are present: 

  • Holes in foliage: Some caterpillars, especially cabbage loopers, bite odd-shaped holes into the greenery. They especially enjoy juicy fan leaves; the holes can be small or several inches wide.
holes in foliage
Holes in foliage made by weed caterpillars
example of caterpillar damage
Another example of caterpillars damage
  • Chewed flowers: Caterpillars like the hemp borer can eat the flowers you worked so hard to produce. As a grower, nothing breaks your heart more than watching bugs eat the resin and tear your precious nugs to shreds.
a caterpillar eating the cannabis plant
A caterpillar in the middle of a bud eating the cannabis plant
  • Brown and dead tips: Caterpillars can cause serious damage to your plants’ health, leading to deficiencies and infestations. It may look like mold, but spotting these critters or their droppings signals a pest infestation.
  • Stem damage: While most common caterpillars on buds eat the flowers and leaves, others seek a more satiating meal: stems. They munch through the juicy material and eventually eat the interior, causing branches to collapse.
a caterpillar eating a cannabis stem
A caterpillar eating a cannabis stem
  • Yellow cannabis leaves: If your foliage starts to develop a yellow hue, it may be a sign of nutrient deficiencies. Along with the presence of caterpillars, yellow cannabis leaves signify that the bugs have reached the stems. The structural damage prevents the foliage from getting sufficient water and nutrients.
cannabis leaves look chewed and yellow
Cannabis leaves look chewed and yellow
  • Stunted growth: Late-stage caterpillar damage causes plants to go into stress, resulting in a size reduction. It also affects your yields as stunted plants won’t produce as big of a bounty.
caterpillars and cannabis
a caterpillar eating hemp

If you’re cultivating strains for indoor growing, it’s unlikely you’ll ever see caterpillars.

How to keep caterpillars off weed plants

Caterpillars on pot can cause significant damage to your plants, and you should get rid of them as soon as possible. The good news is that it’s pretty easy to remove them. However, once the damage is done, it may be too late.

how to get rid of caterpillars on cannabis
Get rid of caterpillars with physical removal

If you spot the signs, follow these protocols to eradicate them:

Physical removal

If there are only a few caterpillars on your plant, or you think they’re too cute to assassinate, you can transfer them via hand removal. Pick them up, place them into an empty glass jar, and transport them to a new location.

removal of caterpillars
Remove as many caterpillars as you can from a plants

Be careful when touching caterpillars on cannabis, as some species are poisonous. It’s best to use thick gardening gloves or a catch-and-release bug trapper. Always wash your hands after handling soil or insects.

Bear in mind that some breeds are nocturnal. If you see holes in your leaves but no caterpillars during the day, you may need to prepare for a nighttime ambush. 

Predator vs. prey

Do you want to learn how to eliminate caterpillars without getting your hands dirty? Give parasitic wasps or praying mantises a try. These predators effectively reduce the number of harmful bugs in your garden.

Plant flowers and herbs like dill, fennel, cilantro, and Queen Anne’s lace to encourage parasitic wasps. They kill caterpillars and use their bodies to lay eggs, so it’s not a pretty sight. Note that wasps can also become pests, so weigh your options carefully.

Praying mantises are less aggressive and unlikely to become a huge problem. These cool-headed hitmen disguise themselves in crops and attack caterpillars. Plant sweet flowers like marigolds, cosmos, angelicas, and raspberry canes to attract them.


The best pesticide option is a natural bacterial spray that harms or chases caterpillars away without hurting your greenery. Most formulas with Bacillus thuringiensis effectively remove them while remaining safe for your crops. 

Do you want to know how to get rid of caterpillars on weed plants? A neem oil solution is an all-natural choice.

Prepare it by mixing 0.17 fl oz. of neem oil with 33 fl oz. of water and 0.07 fl oz. of organic liquid soap. Spray this mixture onto your plants to chase the caterpillars away.

the process of removing caterpillars with natural bacterial spray
The process of removing caterpillars with natural bacterial spray

Neem oil is beneficial against soft-bodied insects like aphids on cannabis. This concentrate has azadirachtin, a naturally occurring compound that repels feasting insects. It’s also suitable if you spot caterpillars and can’t use potent pesticides.

How to prevent caterpillars

Prevention is always better than finding a cure. Do you want to know how to keep caterpillars off weed plants? Luckily, it’s pretty easy. Here are our top tips to keep these chubby critters away:

Natural pesticides

One of the ways to keep cannabis pests and bugs away is by using the neem oil solution discussed above. Another option is nettle tea. All you need is wild stinging nettle, a common weed in the US, especially in damp, shady places.

The tea is stinky, which keeps pests like spider mites and cannabis caterpillars away. Its use is twofold as it deters unwanted critters and keeps your plants well fed since it’s rich in organic enzymes. Here’s how to make it:

You need:

  • Finely chopped stinging nettle
  • Unchlorinated water
  • A bucket with a lid
  • A stick or large spoon to stir
  • Cheesecloth or fine mesh strainer


  1. Put the nettle in the bucket and cover it with enough water to stir.
  1. Place the lid on the bucket, but don’t close it.
  1. Stir the mixture daily and aim to create bubbles while stirring.
  1. After one to two weeks, your nettle tea is ready. Check that the mixture isn’t bubbling to know that the fermentation process is done.
  1. Using a cheesecloth or strainer, separate the liquid from the leaves. You can make compost with the leftover nettle.
  1. Store the mixture in a bucket with a lid. To use it, mix one part nettle tea with ten parts water.
  1. This solution lasts for six months, so discard it and make a new batch if it expires.

Barrier fabrics 

Barrier fabrics are poly-woven solid material that protects your plants from bugs, whiteflies, and other pests. Set the fabric on a wooden frame and lay it over the plants to keep insects from feasting and laying eggs.

Although barrier fabrics are one way of learning how to prevent caterpillars on weed plants, they have some disadvantages. The main downfall is that they decompose but aren’t usually biodegradable. Ensure your unused fabric doesn’t interfere with growing flora.

Beneficial insects

Some insects like ladybugs and rove beetles feed on tiny caterpillars on weed plants. If you grow indoor weed seeds, you can add beneficial insects like insidious flower bugs, as they thrive under artificial lighting.

They also prey on and deter harmful pests from feeding on the greenery or entering their cocoon or chrysalis phase. Plant an array of herbs like dill and flowers like milkweed.

No mercy to caterpillars

Don’t be fooled by their adorable faces; show no mercy if you spot caterpillars during flowering or other plant life stages.

lots of caterpillars on a leaf

Keep them at bay with neem oil or natural pesticides like stinging nettle tea. Use organic bacterial sprays or predator bugs if you have damaged stems or leaves.

When it comes to growing marijuana, nothing guarantees excellent results like quality seeds. Shop our selection of premium cannabis seeds and follow our tips for juicy, potent buds.

AUTHORED BY: Douglas Kester Mr. Kester came to i49 with a wealth of experience. He’s worked in the cannabis industry for more than ten years. As a growing expert at i49, Douglas finds it hard to choose a favorite strain. Instead, he regards each one as unique and full of potential. Douglas finds it rewarding to experiment with specific cultivars and cross-breed to discover a new one. He strongly believes in sharing the benefits of marijuana with as many people as possible to avoid any misconceptions about the herb. Mr. Kester creatively produces information based on what he’s learned and his experience obtained by implementing what he knows. i49 is proud to have Douglas as part of the team.

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