The term ‘leaf miner’ is a common name for a type of pest actually lives inside the tissue of the leaf. These bugs mine through the leaf eating the best parts, and leave a trail of damage behind. These long, winding spots or markings are the signature sign of leaf miners.
A ‘leaf miner’ is not actually a species of bug it is a generic term for the larva/babies of any bugs that live inside leaves and tunnel them to eat (including some moths, sawflies, flies and beetles). Although different types of leaf miners come from different bug parents, the leaf markings look similar.
The lines left on the leaves of your cannabis plants are the the main symptom of leaf miners. Since the insects live inside the leaves themselves you likely wont see them.
More leafminer damage on a cannabis leaf
Solution: How to Get Rid of Leaf Miners on Cannabis Leaves
Now that you know what the damage from a leaf miner looks like on your marijuana leaves, learn how to get rid of them for good!
1.) Remove affected leaves if you can
This wont fix the problem but since the bugs are actually living inside the leaves you are killing them alongside the leaf theyve infected. If you dont want to remove the whole leaf, you can crush the larva by pressing your fingers together where you see a trail.
2.) Spinosad (not for commercial growers)
Spinosad Products (safe & organic) Spinosad products are organic and completely harmless to pets, children, and plants. Spinosad products can be used directly to kill leaf miners by ingestion and should be sprayed liberally anywhere you see leaf miner damage. Although depending on what your ‘parent’ bug is, Spinosad may not be as effective as other treatments, it does work and its very safe for plants, animals and humans!
Recommended: Monterey Garden Insect Spray with Spinosad
Spinosad is a natural bug killer. It comes from a special soil bacteria. It kills leaf miners by affecting their nervous system.
It’s good for organic and outdoor growers. It’s very toxic to leaf miners but safe for many beneficial insects.
Note: Most spinosad products last about 24 hours. So, only mix what you need for each use. Leftover is waste.
You’ll need a mister to spray leaves evenly. Make sure to spray leaves with trails, as it kills larva inside.
3.) Neem Oil
Neem Oil has a bad taste and smell. It’s not good for buds. It may also be harmful to humans. But, it kills many bugs and mold, including leaf miners.
You’ll need a mister to spray leaves well. Neem oil and water can separate.
4.) BT Spray If caused by moth / caterpillars
Some moths lay eggs that hatch into leaf-tunneling larva. These turn into caterpillars and moths. If you see moths or caterpillars, use BT spray right away.
This insecticide has bacillus thuringiensis (BT) bacteria. It kills larva and stops caterpillars from eating. It’s safe for good bugs and kills pests like fungus gnats and worms too.
Use BT spray when you see leaf miner damage and caterpillars or their poop.
If you see big chunks of leaves missing, it might be caterpillar larva. Use BT spray along with treatments for leaf miners.
If BT spray doesn’t work after a few days, it might not be caterpillars. BT is good at killing young caterpillars. If it works, spray again every week until the problem goes away.
Make sure to mist leaves well, both top and bottom. Spray again after rain. BT is safe for humans, so you can spray right up to harvest time.
5.) Beneficial Insect Predators Diglyphus isaea
Diglyphus isaea is a wasp that eats leafminers. You can buy them online to fight leaf miners naturally.
6.) Floating row covers
These are cheap and keep leaf miners away. They let light in and you can water plants through them. They’re good for small plants.
They’re hard to use on big plants. But they’re great for young plants and protect from wind and harsh weather.