by Nebula Haze
Unfortunately, common cannabis bugs and other garden pests can totally mess up your marijuana harvest.
Caterpillars are one of the most common cannabis pests when growing weed outdoors. Use BT Caterpillar spray (works best if you apply with a mister) as a safe and effective way to eradicate them for good.
This page aims to be a comprehensive resource on the different types of bugs / pests / mold that can affect your marijuana crop, along with tips for preventing and solving each problem.
Pests that can affect your marijuana plants include aphids, fungus gnats, thrips, green flies, black flies, mosaic virus, spider mites, caterpillars, inchworms, whiteflies, white powdery mildew / white powdery mold, stem rot, and even mammals such as deer or cats!
If you want a list of safe, all-natural pesticides that can get rid of most of the pests on this list, check out this page: https://www.growweedeasy.com/safe-cannabis-pesticides
- Aphids
- Barnacles / Scale Insects
- Broad Mites
- Bud Rot or Mold
- Caterpillars & Inchworms
- Crickets
- Fourlined plant bug
- Fungus Gnats
- Grasshoppers
- Leafhoppers
- Leaf Miners
- Leaf Septoria / Yellow Leaf Spot
- Mealybugs
- Planthoppers
- Root Rot
- Russet Mites
- Slugs / Snails
- Spider Mites
- Stink Bugs
- Thrips
- Tobacco Mosaic Virus (TMV)
- Whiteflies / White fly
- White Powdery Mold
It’s time to fight back against cannabis bugs, mold and pests!
Quick Tip! Whenever you spray plants with anything, make sure to get the undersides of the leaves too, as this is where many pests like to hang out! A sprayer / mister is also really helpful for spraying leaves.
Get a mister to evenly spray cannabis plants with an insecticide.
Aphids live under leaves and have different forms depending on their stage of life. They are skinny and white when young and fat and plump as adults. Often green, but sometimes other colors like red or black.
These bugs that look like barnacles and stick to the plant on stems and underneath leaves
These mites are so small you will likely never see them even under a magnifier. However, you can tell your plant has been infected because your new leaves will be blistered, twisted and glossy. The overall plant will also be growing poorly and if it’s flowering the buds may turn brown. Broad mites are often mistaken for other problems like nutrient deficiencies, heat stress or pH problems.
When bud rot strikes, certain buds may start looking sickly overnight, with leaves turning yellow and/or bud becoming discolored. When opened up the inside of the bud is dead or moldy.
Caterpillars, Inchworms & Cabbage Loopers
Caterpillars and worms eat holes in leaves, which is typically the main symptom most growers see.
Caterpillars leave droppings that look like black specks. If you see this, you know you’ve got caterpillars.
“Regular” crickets will munch on your leaves while “mole crickets” can tunnel under your plants and disturb their roots!
“Regular” Crickets
Mole Cricket – these can tunnel under your cannabis plants like moles
This is the cannabis leaf damage from a four-lined plant bug (Poecilocapsus lineatus). You can see the adult version of the bug on the lower left. Both the adults and their nymphs make spots in cannabis leaves that usually appear in clusters.
Fungus gnats look like tiny dark flies. They hang around soil that stays wet for long periods of time, and their worm-like larvae crawl around in the wet top soil. Plants start getting sick if a gnat infestation gets out of control.
You’ve probably seen these before, but these seemingly harmless garden creatures will happily eat your cannabis leaves!
These bugs come in almost every color and form, but they all cause “leafhopper burn” on your plants if their numbers get out of control.
Leafhopper cannabis damage (“hopper burn”)
Leaf miners are larva that actually live inside your leaves and tunnel through them to eat!
Leaf Septoria / Yellow Leaf Spot
This fungus causes round yellow or brown spots, with symptoms often starting on lower parts of the plant
These tiny white bugs look “hairy” and are found crawling on leaves and buds.
Each species looks quite a bit different as an adult. Some look like pretty leaves. As youngsters, they create white and fuzzy patches that look like cotton on their butts and on your plants. Planthoppers suck the life out of cannabis plants if they start a colony.
The following are two examples of adult planthoppers (can take many adult forms, though symptoms are the same)
Root rot is a common problem in hydroponic systems though overwatered plants in containers often display similar symptoms. Plants with root rot wilt and leaves may become discolored. In the reservoir the roots turn brown, smelly and slimy.
Russet Mites (or Hemp Russet Mites)
Russet mites are so small you can only see them with a magnifier unless there are thousands of them infesting your plant. They live in the crevices of leaves, stems, or buds.
Slugs and snails usually come out at night, leaving holes in leaves with scalloped edges from their individual bite marks. They also leave slime trails on leaves and on the ground.
Spider mites are often caught from another cannabis grow room, and their bites leave small white speckles all over your leaves. The bugs are so small they can be hard to see, though the best place to look is underneath leaves.
You may see webbing when enough spider mites are living on the cannabis plant.
Various species of stink bug have been known to attack cannabis plants. They lay distinctive patches of white eggs, which hatch into small beetle-like insects and eventually grow into stink bugs.
Thrips leave irregular bronze or silver marks that may look like “dried spit” or tiny snail trails. It is also commonly mistaken for a cannabis nutrient deficiency, environmental stress, or other problem.
Young thrips are tiny and look like fat, squirmy worms living on your cannabis leaves.
It’s not known whether mosaic virus has jumped from tobacco to cannabis plants, but in this article, I’ll share what I’ve learned so far…
Whiteflies look like tiny white moths and hang out under your cannabis leaves.
WPM leaves a white powdery substance that looks like flour or powder on leaves and stems
Don’t see your bug here? Send us a pic!
Jump to…
7 Steps to Cure 99% of Marijuana Growing Problems
Beginner’s Guide to Growing Weed