Get Rid of Caterpillars on Cannabis Plants

Growing cannabis outdoors can be very tricky at times when you have to deal with pest in the garden.

One of the pests that effect outdoor growers every season is the caterpillar.

When you start to find some caterpillars on your cannabis plants you need to take action quickly before it gets out of control.

The best way to prevent an infestation is to be checking our plants daily, see if you notice any signs.

 It is always a good idea to use some type of foliar spray with your plants outdoors to minimize and prevent caterpillars taking up home in your plants.

Let’s check out,

What are caterpillars?

Caterpillars come from butterflies and moths that are flying around is the summer months.

There are many different species of caterpillars, which can affect your cannabis plants.

You may notice them on some of your vegetable garden like, cabbage, kale, lettuce, tomato plants.

I have even had them on my dill plants and they destroyed the plant completely.

If you have an outside light on at night by your cannabis plants then you may be inviting the moths to come in a start to lay their eggs on your plants.

With butterflies they are more present during the day and you may see them flying around.

If you notice them around your plants it could be a sign they are trying to lay some eggs.

Hemp Borer

One of the worst caterpillars to cannabis plants is the hemp borer caterpillar.

The hemp borer loves to chew on the stems and bore its way into the stem and stock.

Unlike most caterpillars species out there that just consume the leaves of the plant.

If you live east of the Rocky Mountains in the US and in eastern Colorado you may be familiar with the hemp borer caterpillar.

Signs of Caterpillars Invasion

Some of the most common signs of an infestation:

  • Eggs on plants stems and branches and even leaves, they look like spots usually black in color.
  • Caterpillar poop or Farss, looks like black pepper on the leaved branches and stems of plant.
  • Chew marks on leaf usually rounded in appearance are a sign something is going on!
  • Stems and branches chewed on for the marrow of the inner branch or stem, you will notice small marks.
  • Stunted growth due to stress of the plant being attacked by caterpillars.
  • Yellowing of the leaves is caused when the leaves are chewed on and damaged the vein structure in the leaf.

WARNING: Watch out for Caterpillars in the buds of your flowers.  When flowering in can be very hard to notice any eggs that were laid on the kolas of the plants. If you do notice any caterpillars it is best to remove the buds completely.

How to prevent an infestation

 Here are a couple of preventative measures to take:

Foliar spray can be used to spray the leaves or soil to prevent moths or butterflies from laying eggs on the plants.

Some sprays you can use is Neem Oil 1-2 tablespoons mixed with a gallon of water. Best to apply the neem oil after dark, as it is harmful to bees.

Screen or clothe barrier for your green house or plants growing outside. This type of barrier can prevent the moths or butterflies from sneaking into your grow and lay some eggs.

How to get rid of Caterpillars on Cannabis plants

There are several ways to remove Caterpillars from your marijuana garden whether you grow in a green house or just outdoors.

Remove any visible worms from your plants and you can place them in a bucket with some water and soap to drown them, or just squish or destroy them how you wish.

Neem Oil is great as a preventative measure of as a means to eliminate them from your cannabis garden. The oil is made from a plant from an area around south Asia and India.

Neem oil is all natural insecticide.  You can dilute it with water. 1-2 tbsp. per gallon of water.

Insecticidal soap can be used by spraying the top of your grow medium such as coco or soil, and as a foliar spray. 

Usually most growers will have this in their garden supplies as it helps with many other pests in the cannabis garden or even vegetable gardens.

Diatomaceous earth can be used as a top layer on your grow medium to deter any caterpillars from crawling up to pots to feat on the stems and leaves of your marijuana plants.

Bacillus thuringiensis BT will be the one that eliminates caterpillars from your cannabis plants for good. Using a Bacillus spray is the best option out there.

One really good thing about BT is that is doesn’t harm bees or other beneficial insects.

This is best used a as a foliar spray, and use as directed by the manufacture. Not recommended for mid to late flower.

Pyrethrum is a natural insecticide that can also be used, what is nice about pyrethrum is it’s also made for a plant called the chrysanthemum.

Lady bugs are great at eating the eggs of the caterpillars, recommended for outdoor growers or greenhouses. The Ladies like to eat the eggs the lady bugs are also great for other pests in your garden.  


Final Thoughts

When you have caterpillars on your cannabis plants they can cause great harm to your plants.

If not taken care of when first noticing the signs things can go from bad to worse.

It’s always good to check your plants daily for anything out of the ordinary, such as black spots on stems or leaves or black peppery like powder.

A good rule of thumb is to use some type of spray in the vegetative cycle to prevent any eggs being laid on your plants.

The best spray to get rid of caterpillars is   Bacillus thuringiensis BT.

Have you had any caterpillars in your cannabis plants? How did you get rid of them?

Let me know in the comments,

Keep Growing!

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7 thoughts on “Get Rid of Caterpillars on Cannabis Plants”

  1. I used BT spray on my second 6patio grown plants this year after caterpillars ate a 1/4 of my first . I also unleashed 2500 ladybugs . Between the two I totally obliterated the caterpillars.

  2. This is my first grow, as it just became legal in my state. It was growing beautifully outside until yesterday, when I saw the buds on one plant were falling over, and squishy looking. That’s when I discovered the caterpillars! Is there any use for the damaged buds?
    Thank you for this article

    • Great question. I would check to see how damaged they are. maybe use a pocket microscope to see if there are any other bugs in the bud. you may be able to salvage it. But I would not recommend smoking it.

  3. I’ve been picking them off whenever I see them and tossing them. Used to have wasps swarming around in backyard but not so much this year . They used to keep them in check for the most part. I will follow your advice and start spraying during veg state. Thanks


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