cannabis worms

Caterpillars & Inchworms

Stop Caterpillars From Attacking Your Cannabis!

Caterpillars. Argh. Sometimes the first sign of caterpillars / worms / cabbage loopers is just seeing chunks of your leaves missing. You may also see clumps of black/brown “dirt” on your leaves, which is caterpillar poop. Lastly, you may actually catch a caterpillar munching on your leaves. It can be so angering to catch them in the act!

Zebra caterpillar on a cannabis leaf, picture by Whitney Cranshaw of Colorado State University

Saltmarsh caterpillar on cannabis leaf, picture by Whitney Cranshaw of Colorado State University

Another saltmarsh caterpillar on a marijuana leaf, picture by Whitney Cranshaw of Colorado State University (thank you. )

You’ll see chunks of your leaves missing from the caterpillars devouring your leaves

caterpillar leaf damage pic by molpes

Caterpillar Droppings on Leaves

You Actually See Caterpillars, Inchworms or Cabbage Loopers

caterpillar pic by Waterproof

Proven Caterpillar Remedies

  • Caterpillar “BT” Spray (safe biological insecticide) – This biological insecticide contains the bacillus thuringiensis (BT) bacteria which kills larva and prevents caterpillars from being able to eat. This is one of the most effective ways to kill caterpillars, and won’t hurt most beneficial insects. As a bonus, it also kills other cannabis pests like fungus gnats, worms and moths. Apply a caterpillar BT spray as soon as you see leaf damage, caterpillars or caterpillar poop. BT sprays work best on small caterpillars that are actively eating your leaves. Repeat every week for as long as you’re still seeing caterpillars, though you can give BT more often if there’s a heavy infestation. Make sure to thoroughly mist both the tops and bottoms of leaves, and apply again after a heavy rain (since that will wash the BT away). Since BT is harmless to humans, you can use BT products up to the day of harvest! One thing to keep in mind is BT spray almost instantly stops caterpillars from being able to eat, but doesn’t kill them directly. So although you may see the caterpillars alive and apparently unharmed after spraying, the BT is still doing its dirty work.

  • Spinosad Products (safe & organic) – Although not as effective against caterpillars as a BT product, Spinosad can be a good choice, especially if your plants are also suffering from other insects like aphids, spider mites, thrips or white flies since this will attack all of them at once. Spinosad products are organic and completely harmless to pets, children, and plants. Unlike many insecticides, you can spray properly diluted spinosad heavily on leaves and roots with basically no negative effects. Spinosad products can be used directly to kill caterpillars on contact, but can also be used when watering plants to systematically kill caterpillars via the soil.Spinosad is an organic insecticide made from the fermentation of a specific soil bacteria (actinomycete Saccharopolyspora spinosa) and kills caterpillars via ingestion or contact by effecting the insect nervous system. Spinosad can be a good choice for organic and outdoor growers, because it is very toxic to caterpillars, but is less toxic to many beneficial insects.Note: Most spinosad products are effective for only about 24 hours after being mixed with water, so only mix as much as you will need per application. Anything left over will be waste.

  • Avoid butterflies and moths! Although these beautiful creatures look great resting on your cannabis plants, they lay eggs that hatch into caterpillars! Don’t let them hang around your garden!

Learn how to identify and get rid of caterpillars (and other little worms) and prevent them from ever attacking your cannabis again!


Caterpillars are one of the most voracious and harmful pests that can affect our plants during the outdoor growing season.

It is a very aggressive pest that, if it is not controlled in time, will cause irreversible damage to our plants. But it can be identified, prevented and eradicated if we are fast and careful. As always, prevention and early detection is essential to avoid the serious damage that this pest will cause to our harvest.

  • 1 What are caterpillars?
  • 2 How to avoid the caterpillar attack.
  • 3 If prevention has not worked.
    • 3.1 1. Remove them manually:
    • 3.2 2. Biological control:
    • 3.3 3 To pulverize the plants:
  • 4 Watch out for outdoor crops.

What are caterpillars?

Caterpillars are the larvae of the lepidoptera family, which after their metamorphosis turn into butterflies (moth moths). There are more than 10,000 types of caterpillars but all are characterized by a long, segmented body, six legs and five pairs of pseudopaths with small hooks. They are polyphagous, so they feed on different types of plants.

The plague of caterpillars begins when butterflies and moths lay their eggs on our plants, so if we observe these animals hovering around our crop is a bad sign.

The life cycle of the caterpillar is very simple: once the eggs hatch, the caterpillars emerge, feeding on the leaves and flowers of our plants until they reach the right size to move on to the pupa phase. After 1 week to 1 month, the butterfly emerges.

The damage of the caterpillars is visible from the moment they hatch their eggs, since they feed without stopping, and we will be able to observe bites in our leaves and flowers. In addition, they have a predilection for flowering plants, which causes that their attacks favor the appearance of moulds and rottenness in the buds, a real disaster.

Caterpillars like to be hide in the underside of leaves and stems, so we must check and pay special attention to these parts of the plant, as well as the remains of the excrements that will be left behind.

How to avoid the caterpillar attack.

Obviously, the best thing we can do to avoid severe damage to the caterpillar is to prevent it, but how can we prevent it from appearing? Here are a few tips to help you avoid the caterpillar attack as much as possible:

  • 1. Constant and exhaustive revision of our culture to make an early detection, as well as to observe that we are not possessive butterflies and moths for our plants.
  • 2. Cultivate plants such as thyme or basil that repels them or cabbage or soybeans for which you have a predilection.
  • 3. Colocar trampas impregnadas de feromonas femeninas para atraer y atrapar a los machos e impedir que sigan reproduciéndose.
  • 4. Use Bacillus thuringiensis: bacteria that is used to treat caterpillar plague once we are already infested but can also be used as a preventative.

If prevention has not worked.

If prevention has not worked and we have this annoying plague in our crop, not everything is lost, although a quick detection will help a lot, as caterpillars are voracious devourers and will not stop eating until they reach pupa.

effect marijuana worms

The direct damage caused by this pest deriving from bites on leaves and buds, together with indirect damage caused by bites on buds that cause mould and rot, cause serious problems in our plant leading to death.

To treat caterpillar plague in our plants we can use one of these methods:

1. Remove them manually:

It may seem a bit rudimentary and even rather unpleasant but removing all the big caterpillars we can with our hands helps in eradicating this plague.

2. Biological control:

Biological control involves the controlled introduction of natural predators of the pest that we want to eradicate, so that they are responsible for eradicating it.

It is a totally ecological method in which you do not need to spray or water our plants with any product. The caterpillar’s natural predators are Coccinella septempunctata, commonly known as ladybird or Orius spp, a predatory bug of this type.

3 To pulverize the plants:

Spraying the plants with Bacillus thuringiensis, the same bacterium that we mentioned in the prevention section, is an effective anti-caterpillar remedy that we can use once we have been invaded by this pesky plague.

This bacterium penetrates the plant tissue that the caterpillar later ingests, causing irreversible damage to its digestive system as it contains toxic substances for the caterpillars.

Watch out for outdoor crops.

In short, we must be vigilant when growing outside crops for this type of pest that can quickly kill everything. We must use prevention methods and frequently observe our plants to make a quick detection and act as soon as possible by trying to get rid of the caterpillar before it kills our crop.

You may also be interested in these articles about the red spider mite or the Whitefly.

1 Comment

TINA VAIL 23 September, 2020, 6:48 pm

i just want to know how to get rid of and to kill the budworms.i have got the neem oil and it says it has bt in it

Caterpillars are one of the most voracious and harmful pests that can affect our plants during the outdoor growing season. It is a very aggressive pest ]]>