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What To Do To Keep Caterpillars Off Your Marijuana Plants


The most harmful of these soft segmented pests are the Corn Borer and Hemp Borer. They eat the marrow within the stalk creating stem cankers, which weaken the plant.  A heavily infested cannabis plant can collapse.  A mere five to twelve larvae can literally destroy one plant.  Equally damaging are that the holes bored into the stems by Corn Borers leave an open door for other sap sucking bugs, resulting in the life literally being drained from the marijuana plants.  Hemp Borers attack the flowering tops.  This is one activity you want to nip in the bud right away!

Oftentimes, stem boring caterpillars are not detected until the damage has already been done because they wreak their havoc from the inside of the plant.  Examine the stems for holes with surrounding brown trails.  Chances are you have a problem if you see visible holes on your cannabis.  The only effective treatment for stem borers is to cut them out of the plant.  If the plant does not ‘come back’, make a clean cut at the base of the trail, completely removing it to ensure no further damage. Download my free marijuana grow bible for more tips about pests and marijuana plants.

All caterpillars cause damage to cannabis plants; they love marijuana!  The caterpillars of which we can all readily recognize eat the leaves and flowers of all plants; pot is no exception.  The damage they cause is readily visible as indicated by the appearance of chew marks left on the leaves.  Introducing parasitic wasps will allow nature to take its course in eradicating caterpillars.   Chances are they will appear on their own once the presence of caterpillars is sensed.  Mother Nature has an innate sense of when to send in the troops.   Parasitic wasps lay eggs on the caterpillars’ bodies.  When the eggs hatch, the creepy crawly becomes a gourmet delight for the upcoming wasps.’

Another control, compliments of Mother Nature, is the praying mantis.  This amazing stick like bug may not thrive in all areas, but if you have them in yours, help is on the way.  Praying mantis’ eat caterpillars and will not leave the plant until it has cleaned its plate, so to speak.

You can further control the caterpillar population by applying a neem oil spray.  It is best to spray after the sun goes down or on a cloudy overcast day, as the sun renders the concoction ineffective.  Spray the tops of the plants and at the base to deter caterpillars from climbing up from the ground.  It is not necessary to saturate your plants, but coat them well.  If any caterpillars are not killed on the spot, they will die as they travel through the plant and into the path of the oil.

To make your own neem oil spray, pour 1 to 1 ½ teaspoons liquid dish washing soap to a gallon of warm water.  Add one ounce of neem oil to the container and shake well.  Pour mixture into a spray bottle.  Do not store any unused portions, as it loses its potency after four to eight hours.  Apply once a week until there is no longer evidence of the caterpillars in your garden.  Neem oil can be purchased online or at any garden center.

Of course, you can always hand pick caterpillars off your plants.  Just make sure you destroy them or they will be crawling right back onto your precious plants.

If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.

Source: ILoveGrowingMarijuana.Com



About Author

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.


  1. LOL, I did to. Was showing a tight friend my hanging harvest and a one inch green bastard comes inching along my twine at eye level. Greatly enjoyed torturing with scissors, would’ve waterboarded too if I could I was so pissed. Ended up making two gallons of 151 tincture from the affected/suspect strains (I’m not vaping some effin worm, worm shit, or mold left behind) and fortunately still yielded a sizeable amount of very sweet 24% THC indica bud to vape until December.

    BTW Tincture is way under-rated for medical and adult use. Taking 151 vodka (or rum) or the real good 190 in other states sublingually with delta 9 at 24% and add raw honey so you don’t shred your tongue. I’m up to two tbls and it’s a fast turbo medible with an alcohol chaser. Or try 1/2 cup shot (hits you later) My overall tolerance keeps building and building and I may burn through my vaping stash before December from chugging tincture.

    Back to bugs. I’m going with weekly Neem/Spinosad right from vegetation transition, maybe even a few weeks earlier this year. For sure if I see effin moths in the air. Neem has been tremendous this winter on my mama/clones problems with spider mites that my harvest brought indoors (another lesson learned) and every CA sunny day they keep asking me to get in the dirt outdoors. Obi-Wan: “[They] will learn patience.” From: Star Wars II “Attack Of The Clones” The irony. Lmfao

  2. Dennis "Rock hard" Rodman on

    Bro I had a caterpillar problem , soo bad I took a pic for Instagram and sure enough a caterpillar was in the photo , and also after my harvest when i was curing the bud I was able too save , I swear they when even in that smh

  3. These **ckers got me 5 days before harvest this year! Won’t/can’t use bT and no way touch Neem this close to chopping. As Robert says, cut your losses, they’re inside–probably your biggest colas (watch for pistils turning totally brown over night) break apart your buds and you’ll find the **fucker(s). Some were mere mms long, a couple that wiped my best Tahoe OG tops were an inch long. As I have read, moths deposit the eggs where they literally are grown/protected as the plant grows, thus they’re inside (though I don’t dispute Robert’s boring method, I found no evidence). And once inside, don’t waste your money trying to spray or trust IPMs. Next year, praying mantises and prophylactic bT every 3-7 days at the first moth or egg siting. I took a 33% loss. Never again.

  4. dude i was inspecting my outdoor garden whem to my chrgrin i pealed open my bigest cola to finde some (2) catapillars. stoned off ther ass on my frosty ass tricomes how do i kill the rest cuz i still got 2 or 3 weeks of flowering to do. please someone help me

  5. Gerardo Godinez on

    Hey everyone I need some help. I walked out this morning and I seen a caterpillar eating one of my nugs. Plant looked ready to harvest so I cut it down so it can dry. I have three more plants and not sure if they have caterpillar.. What should I do take them down and dry them or risk it and keep them up?? HELP!!!!!!!!

  6. I have 5 outdoor plants that are being eaten by caterpillars i want to do the dish soap mix with neem oil however you stated that u cant store it because it loses its potency after 4 to 8 hours. Can i store the gallon jug, or i have to discard both from the spray bottle and the gallon container i mixed it in?

  7. are those the little green inchworm looking-like things that chew holes in buds and cause mold and rot? Hate those fuckers!

  8. Johnny oneye on

    Bt is Monsanto product
    GREEN light caterpillar killer
    I think is the name
    or Safer caterpillar spray
    BT has to be applied every few weeks.
    These are pesky little creature that will eat your biggest colas!

  9. Johnny oneye on

    Cali is prime for cutworms.
    Neem wont do the trick .add BT
    As much as I hate sprays its unavoidable outdoors.
    Crop loss sux

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