Leaf Miners on Cannabis: How to Identify, Prevent, and Get Rid of Them

Leaf miners on cannabis plants are attracted to the herb in much the same way as humans are. The only difference is that instead of waiting for the buds to reach full maturity, they snack on new leaves. As a result, these pesky bugs affect further growth and yield sizes.

Keep reading to learn what these insects look like and discover how to spot and stop an infestation. We also present pictures of leaf miners, damage to cannabis plants, and what products are best to use to eliminate them.

Ready to ensure your crops stay critter-free and produce delectable marijuana buds efficiently?

Let’s jump in.

What are leaf miners, and what do they look like?

Cannabis leaf miners are not a single species of bug. They’re a collective of larvae from various parent bugs, mostly flies, moths, sawflies, wasps, and some beetles.

The tiny larvae vary in color from white through yellow to light green and measure 0.08–0.12 inches long. These insects munch on leaf cells, devouring the juicy green parts within the epidural layers of the cannabis foliage.

This action affects the plant’s capacity for photosynthesis, which can slow growth in extreme cases. The larvae gorge mainly on the softer cells with less fibrous cellulose. Leaf miners progress through four stages in their lifecycle: egg, larva, pupa, and adult.

When they hatch, the young larvae don’t have legs and immediately burrow into the leaves and start to feed. The walls of the foliage provide the youngsters with a haven and an accessible food source.

Leaf miners on weed emerge from eggs usually laid on the underside of a plant’s leaves. Growers should check their crops every week to keep abreast of potential infestations.

The larvae feast on the cannabis foliage until they’re ready to pupate. The larval structures break down, and adult appendages like wings or legs appear for the first time. Hormones cause pupation, and when complete, the young adults emerge.

They split the pupal skin, secrete a softener, or chew their way out, with mature flies looking like small houseflies. Depending on the species, they complete their metamorphosis within the leaves or the soil beneath the plants.

When sexually mature females dig into the blades to lay their eggs, a sap gets released that attracts ants and flies. It invites other pathogens and problems into your cannabis plants and could be a prelude to further troubles.

The signs of a leaf miner infestation on weed plants

Cannabis leaf miners leave a tell-tale trail similar to a scribble, making identification reasonably simple. The tunnels or tracks are feces left behind by the yellow or white larvae as they ravenously tunnel their way through the chlorophyll-rich blades.

The irregular white or brown lines can lead to blotches on the leaves, in extreme cases causing them to wilt and fall off. The reduced potential for photosynthesis means slower vegetative development with curled or distorted leaves.

While usually a minor inconvenience for matured crops, these bugs can kill new seedlings. The larval stage is when most damage occurs, and they typically attack the freshest leaves. Even a substantial infestation is unlikely to kill your mature plants. 

An outbreak may cause leaves to fall to the ground prematurely, hampering growth and shrinking yields. These cannabis bugs generally only cause cosmetic damage and don’t target older, tougher foliage. 

Adult marijuana leaf miners don’t feed on foliage like the larvae. You seldom find these pests indoors, and outdoor issues rarely affect the plant’s health and production. Leaf miners can’t bite humans. 

In short, cannabis plant symptoms include:

• Squiggly brown or white lines on leaves
• Adult flies, sawflies, beetles, or moths hanging around your crops
• Brown leaves that may fall off prematurely
• Dry blotches on leaves
• Curled or distorted leaves

How to kill leaf miners on cannabis leaves

If you’re growing your own crops, you need to know how to kill leaf miners in cannabis. While these pests mainly produce aesthetic damage, severe outbreaks can compromise your final results.

The easiest way is to track and squish the larvae with your fingers by pressing on the leaves. This method only works in the early stages with limited pest numbers and minimal damage.

In more comprehensive circumstances, experts contend that removing or pruning affected leaves is best. Remember to dispose of them away from your crops to avoid reinfection. Extensive pruning can delay the harvest.

Early detection makes it much easier to address leaf miners on weed plants before they attack your crops.

In more extreme cases, sticky traps with vibrant colors are so attractive to the adult bugs that they can’t help themselves. This trick doesn’t affect the larvae but prevents the adults from spawning the next generation.

Spinosad is an organic insecticide that affects miners and whiteflies when they ingest it. It’s made from soil bacteria mixed with water and sprayed on infected plants. This solution kills pests while leaving beneficial bugs unfazed.

Leaf miner prevention and control

All growers should know how to kill leaf miners on marijuana. Natural and organic methods produce fewer negative impacts on the soil and environment. These techniques also wipe out other pests like nematodes and mealybugs.

You risk creating genetically resistant miners with more significant issues by using chemical pesticides. These synthetic compounds may damage the soil and lead to human health problems. The pests live inside the foliage, so many believe external spraying doesn’t work.

The best way to avoid leaf miners is to maintain a clean growing environment with healthy soil enhanced with cannabis fertilizers. Remember that female adults only lay their eggs at temperatures above 77⁰F. 

We assess some of the best preventative measures below:

Beneficial predators

Growers can introduce beneficial predators into their garden to tackle leaf miners in marijuana. A parasitic wasp called Diglyphus isaea stings the larvae within the leaves, laying eggs next to the corpses to provide food for their young when they hatch.

Other predators that can reduce leaf miner effects include:

• Praying mantises
• Rove beetles
• Ladybugs
• Green lacewings

Neem oil

This organic pesticide is made from the pressed fruit of the neem tree, found widely in southern Asia. It’s a popular product used by growers around the world.

Mix a teaspoon of neem oil with about 33 fl. oz. of warm water and a few drops of insecticidal soap. Use a mister to dose the affected plants. Pay particular attention to the undersides of the leaves to neutralize any eggs.

While it irritates pests, beneficial organisms suffer no adverse reactions. Neem oil ousts leaf miners and aphids after just a few applications and also prevents several other cannabis plant problems. 

Don’t use neem oil solution in the final three weeks of flowering, and avoid spraying it on the budding sites. It can leave an unpleasant smell and taste on your cannabis buds, and there’s some evidence it could be harmful to human consumption.

Bt spray

If you think your crop has moth or cannabis caterpillar damage, Bacillus thuringiensis (Bt) helps. The biological insecticide contains Bt bacteria that kill leaf miners on your marijuana plants and stop caterpillars from eating them. It also gets rid of other cannabis pests.

Beneficial fungi, herbal teas, and horticultural oils or pesticides can also wipe out a leaf miner infestation. 

Expert growers typically select marijuana seeds for beginners for their ease of use and resistance to pest attacks. High-quality cannabis seeds have reliable and stable genetics that fight off disease. Always buy your cannabis seeds from trusted sources. 

Bye-bye cannabis leaf miners

Finding leaf miners on a cannabis leaf isn’t the worst cultivation problem you’ll face, but it may impact efficiency and your final results. These chlorophyll collectors may diminish optimal development, which delays and dents your yield, so don’t let your guard down.

Our seed bank has a wide range of high-quality cannabis seeds in the USA. We’re the perfect place to find top-tier marijuana, so buy your weed seeds today, and we’ll discreetly deliver them within a few days.