Caterpillars on marijuana plants

Caterpillars love marijuana plants! Corn Borer and Hemp Borer are the two most destructive caterpillars. These pests will diminish the strength of your plant by eating away at the marrow inside the stalk causing stem cankers to form. If the plant is really infested it will break down.

Read this article and learn how to identify caterpillars on your marijuana plants and how to get rid of them.

Signs of caterpillars

All it takes is about five to ten caterpillars to demolish your plant. You can easily identity their damage by the chew marks left on the leaves. Observe the plants stems to see if there are holes with brown trails around them. If you notice visible holes on your plant, then you most likely have a problem.

What’s even worse is that the hole Corn Borers carve into the stems creates an open doorway for other pests that will completely suck the life out of your marijuana plants. Hemp Borers will damage the buds (see picture).

Effect stem boring caterpillars marijuana plant
Effect stem boring caterpillars marijuana plant

Stem boring caterpillars do their damage from the inside of the plant so, they can go undetected until it’s too late and the harm is done.

Also read Marijuana pests & bugs – Control and identification

How to get rid of caterpillars

You can simply rely on nature to eradicate caterpillars by having parasitic wasps around. Mostly likely they will come all on their own as soon as the sense caterpillars are nearby. These wasps will lay eggs on the caterpillar’s body and when they hatch, the caterpillar becomes food for them.

Another way nature can assist you with this is the praying mantis. These insects love eating caterpillars and will remain until all of them are fully devoured.

a green caterpillar on a marijuana plant

When it comes to stem borers the only way to really get rid of them is to cut them out of the plant. If the plant doesn’t revive itself, then completely remove it by doing a clean cut at the bottom of the train. This will guarantee no further damage.

A complete plant defense system can help protect your crop from diseases and harmful pests. Grab our Plant Protector set today!

Marijuana Plant Protector Set

Buy plant protector set

  • Protection against diseases and pests
  • Consists of three 20 ml bottles
  • Enough plant protection for 20 plants

Neem oil spray is excellent for caterpillar control. Use this once the sun has gone down or on an overcast day. The sun will make the solution useless. Spraying the tops and base of the plants. Don’t overdo it, just cover it really well.

Making your own neem oil spray is easy, just pour 1 to 1 ½ teaspoon liquid dish soap into one gallon of warm water. Pour in one ounce of neem oil and shake well. This concoction will lose its strength after 4-8 hours, so it’s pointless to keep what you don’t use. Do this once a week until all caterpillars are gone. You can buy neem oil at a nearby garden center or get it online at this link here.

List of marijuana plant symptoms

How to recognize marijuana plant symptoms caused by caterpillars:

  • Holes with brown trails around them
  • Chew marks on the leaves
  • Yellowing on the top leaves
  • Holes and damage to the stems

Remember caterpillars are marijuana lovers! If you see any signs of these, you definitely want to do something about it immediately. These pests will destroy and potentially suck all the life out of your plant.

Marijuana plant symptoms
Marijuana plant symptoms

Plants with strong genetics have less chances of getting sick and are less vulnerable to pests and diseases. I have created multiple grow sets which features all you need in order to grow healthy plants from seed to harvest!

buy white widow marijuana grow set

Get your grow set

FAQs about caterpillars on cannabis plants

What are some ways to eradicate caterpillars on cannabis plants?

Having parasitic wasps or a praying mantis around the plant, cutting the affected stems, or spraying with neem oil are some effective ways to deal with caterpillars on your weed plants.

How many caterpillars does it take to take down a marijuana plant?

All it takes is about five to ten caterpillars to demolish your plant.

What plant symptoms should I look out for to know that my plants have been infested with caterpillars?

Some of the most common caterpillar symptoms include chew marks on the leaves, holes and damage to the stems, and yellowing on the top leaves.

Practice and learning are all you need to grow marijuana like a pro! Let my blog help you get started.

Have you had caterpillars on your marijuana plants? Please share your experience or leave questions in the comments.

Download my free Grow Bible to learn more about dealing with pests on your marijuana plants.

Happy growing!


Avatar for Robert Bergman

Mr Robert Bergman PhD


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

  • Pinterest

47 comments on “Caterpillars on marijuana plants”

  1. Hi Nick,

    Thanks for your message. Remove them from the plant and try some neem oil spray!
    Keep us posted on if it works! And let us know if there’s anything else of course.
    Kind regards,

  2. I found 2 small green catipillars that began eating in 2 different branches of out door bud . Was Need a good Home remedy that might work

  3. I Grow a few Plants outside each year and each year i get caterpillars chewing my buds and stems. One year i did not notice them and they ruined my harvest. I managed to harvest but the flavour was ruined. Tasted like caterpillar shit! Yuck. Anyway, this year i did notice and so far have squashed over 70 on one plant. It’s a time consuming job. They are Often deep in bud, leaving their poo in the bud which when it rains begins to rot the bud. Having to part the buds to find pest left my thumb and index finger sticky black but unusable.
    The search will continue daily. They’re even still On my drying plants.
    Most sprays available are contact types which is very difficult when the pest is so deep in the bud.

  4. Hi Nick,
    Thanks for your comment. Praying mantises are actually good for you plants, as they can help protect it from other pests! So that’s good!
    Happy growing,

  5. First time grower and grow outdoors and i found on Caterpillar that I removed and a couple days later i saw a praying mantis

  6. I’ve grown for at least 40 years inside and and out I like outside the best because it’s cheaper, easier and I get more quantity anyway my strategy has always been to grow a lot to get a little so I never paid much attention to the bugs but now my space is more limited I planted 8 autos at the end of April and they were doing great then I noticed the tops were dying I saw a little white moth on a plant I’d seen them before on previous crops I think they lay eggs in the tops then I cut one of the stems off and it was hollow I started pinching all of stems and branches and they would collapse all 8 plants were infested then I started looking through the tops and found a little worm I was looking for something bigger so I figure it’s a corn or hemp borers my last outside crop at the end of the season I could shake a branch and a cloud of tiny moths would flutter off I sprayed soapy water on the plants I don’t know if it did any good so anyway my theory at this time is the worms that are eating my stems out are the larvae of those little white moths that have reeked havoc on my crop for years I got some organic catapiller killer I’ve been spraying on my plants
    Any thoughts

  7. I had small 1 inch long caterpillars or army worms or borers, anyway, I did not see any sign of them until the tops of some colas dried out. The top simply came off and you could see a hollow stem with white dropping. I also noticed some dried out calyxes on the side of a bud. The worm was deep inside the cola at the stem area. I thought the high temperature here in Az. Was burning the buds, no it was pests. So I cut the top off down to solid stem and froze the bud for ice hash. So if your big giant colas start showing a dried out or dying spot, dig into that cola and find the worm. The buds are very resilient and wont damage if the plant is otherwise healthy. Its like digging into a pine cone. Just spread the calyxes. Hope this helps someone.

  8. Hi Robert! My plants are only a couple of weeks away from harvest, and the caterpillars are out of control! How late can you spray before harvest? I’m trying to grow everything in the sun and organic.

  9. Hi! I noticed some bud-Rot developing at a lightning-fast pace on my plants the last week of August, and remembered my friend telling me that he had bud-caterpillars on his crop, and used Thuricide on them. I did some research, and saw that SPINOSAD is also an organic bacteria-based product but with two or more weeks of staying-power—(rather than Thuricide’s 1 to 2 days). My infestation was bad, so I thought that I should apply them both, tegether in the same sprayer. I made the mistake of pouring 1 quart of Spinosad, (pre-mixed from a spray bottle because I could not find any concentrate), then pouring in 1 tablespoon of Thuricide and three quarts of water filling my 1 gallon sprayer. The directions for diluting the Thuricide called for one gallon of water, but I was unable to add a 4th quart because, again, my sprayer held only 1 gallon. My brain was pretty-fried after pulling an all-nighter picking caterpillars off my plants, and I just figured that I could substitute that initial quart of premixed Spinosad for water—(as it WAS liquid after all). Spinosad can be applied-heavily, but the Thuricide was supposed to be just lightly-misted. Well, these caterpillars were ravenously-munching deep inside the bud-clusters , so I thought that if I didn’t completely-saturate-the colas, that there would be nothing of the plants left. Well, it was either the wrong Thuricide-ratio, the applying of both pesticides simultaneously, or the heavy-saturation—(in conjunction with the trauma of the bud-clusters being spread wide-open and picked-through so that I could remove the caterpillars), that I think did-them-in. Within two hours of spraying, my absolutely-gorgeous, plump, wonderfully-fragrant and crystallized-colas were all-shriveled-up to 1/2 their size, and all the hairs that had appeared stark-white and standing-at-attention 2 hours before were now all orangey-brown and withered. All that was left to the once-mighty-colas was a nasty burnt-smell! It was as if someone had dropped napalm on my plants overnight!!!!! Prior to my spraying, I had researched for one whole day whether it was OK to spray both of the insecticides simultaneously, but I could find no articles on the topic whatsoever—-anywhere! Seemingly as I am the first person writing about this topic, I would be extremely-pleased if my experience was not in vain, and hope that both you commercial and individual-growers alike will benefit from my experience and make it through to see a bountiful harvest without making the same mistake!
    P.S. From my research, I discovered that Spinosad can safety be applied——-via water throughout the grow——to systemically-prevent caterpillars from EVER setting foot on your crop! However, protection by this systemic-approach does not develop right-away. If I we’re still growing this season, I would start doing it AT ONCE to all of my plants, ALSO, I would experiment on at least ONE PLANT——-by lightly-misting the top and underside of the leaves as well as the colas with THURICIDE to see if a plant can tolerate them both this way. This should give you a very-strong long-term protection from Spinosad, plus the immediate “shock-and-awe” of the supposedly more effective Thuricide!

  10. I thought I had caterpillars as all my nodes grow and then disappear some of the leafs look like they are holding on by a thread I need help no one seems to no what’s happening

  11. Found one caterpillar on one plant
    Searched for 3 hrs. To rid of anymore. Have to clean leaves of poop. Second plant has signs of poop but no sigh of caterpillar
    What do I do with my buds to protect?

  12. it is almost harvest and signs of caterpillers are appeariing in my outdoor garden. .tiny ones in the buds killing them off. huge ones…several all sizes and you have to Practically destroy the bud to find them. what can i do to kill them off when they are deep in my flowers, without ruining my crop, and the taste, and how can i prevent them from even being there next year….

  13. T,

    You would be helped in real time by joining our support forum at:

    There are many other options aside from Neem oil.

  14. T,

    Once every week depending on the pest. Never use Neem oil in late flower or buds will taste like “poop” 🙂

  15. Mary J.,

    Read the directions. There will be a paragraph that tells you how long before harvest that you can use the spray. 🙂

  16. Please help!!!! My whole crop is infested with tiny caterpillars. We’re picking them out one by one and sprayed neem soap spray. Do you also need to cut out brown spots as well? Can you still smoke or is it all ruined? Freaking out!

  17. How much time should there be between spray (Safer Caterpillar Killer) and harvest? A week a couple of days?

  18. Anyone using Spinosad? Sounds very promising. I talked to an extension agent in the middle west who said corn earworm were HORRIBLE this year. I got them first time ever in over 30 years of outdoor projects.

  19. can I dust the plants with food grade D.E. or just the ground around the plants. cause i dont want to make a huge mistake.

  20. I already answered this somewhere but, here goes. No. Do not rinse off the organic and dissipating neem oil. It might be OK to give the plant a tepid shower at harvest time as long as you have 4-6 fans to dry it off afterward. 🙂

  21. Terrance. No you do not rinse off the neem oil. It will dissipate over time. I hope it all works out for you. Thanks for sharing. 🙂

  22. Well i picked off all the catapillars i could find on my plants then sprayed it down with the soapy water then rinsed it down then waited till this evening to spray it down with the neem oil spray. I have my fingers crossed i did everything i read on this site so thank you everybody for all the input and help .time will tell . Oh yea quick question was i supposed to rinse off the plant after the neem oil application ???

  23. Whats the name of the product you are using to rid yourself of catapillars ???

  24. Maggie,

    You could also be proactive by dusting the area with Food grade CODEX Diatomaceous Earth. – I❤️GM

  25. Maggie,

    Best thing you can do is to monitor the plants and be ready with insecticidal soap or some other safe option. Happy growing 🙂 – I❤️GM

  26. Does anyone know if the birch borer will attack marinara plants? I have a lovely birch that I suspect may be infected and it is pretty close to where I would plant my plants outside

  27. I had a bad problem with those bud eating caterpillars they got inside the biggest buds I have ever grown 19inch buds and when I noticed some parts of the buds didn’t look right i touched it to feel it and it just crumbled and so did my heart!! That’s when I found them and became a surgeon dissecting every bud removing the worms by hand, them worms destroyed at least 3oz worth!! By the time I was done my plants looked like they had a kemo treatment…

  28. Spinosad is an ingredient in approximately 80% of all pesticides. When using a produvt such as Spinosad; It is advisable to read and follow the directions on the bottle. Each pesticide is different.

    If you cannot figure out from the label instructions as to whether it is safe to use on plants you plan to ingest; You are advised to call the manufacturer of the product..

    On the label. Find out what it says about eating produce treated with Spinosad. Many products used on produce contain Spinosad.

  29. Last year I lost all four of my plants due to caterpillars damage. So this year I brought a mosquito netting to cover my plants. All six of my plants are budding nicely and no sign of caterpillars. YEAH!!!!!

  30. Best thing to do about “Caterpillars”; Immediately remove by hand. In some cases an insecticidal soap can work to stifle the production of further generations. It may take 2-3 applications, spread out over 304 weeks to catch up with larvae, or hatchlings; Etc.

    Using an garden duster to apply Food grade CODEX Diatomaceous Earth will also eradicate these pests, and any other pests with a soft exoskeleton.

  31. I have had a terrible time with caterpillars in the past. This year I have been using Safer brand caterpillar killer…bacteria BT that targets only caterpillars. I apply in evening apx every 10 days…not a single caterpillar this season!!

  32. Hey john, my plants were hit by caterpillar’s as well! It has been a nightmare on the east coast this year, we are down about 7 inches of rain. We had many day’s of temps in the mid to high 90’s here in the Carolina’s.

  33. […] Unfortunately, even caterpillars that stay on the exterior of your plant can still ruin your crop. Caterpillars are strongly attracted to cannabis, and they will actively seek it out as a food source. Outdoors, you can get help from wasps and praying mantises, but there are number of organic deterrents you can use as well. Read more about Caterpillars on marijuana plants […]