How to Get Rid of Leaf Miners on Cannabis?

Does your plant’s leaves look like a kid has scribbled some postmodern doodles on the surface with a white marker? Don’t worry, no kid has invaded your cannabis garden, it is a leaf miner invasion. It may not look serious right now, but you should be worried. 

Leaf miner invasions start as a simple, seemingly-harmless problem that can quickly turn your thriving, lush plant into something that doesn't grow, droops, and eventually dies. 

But what are leaf miners and how are they dangerous for your cannabis plants? 

Read on to know all about getting rid of leaf miners on cannabis plants. 

What are Leaf Miners? 

Leaf miners, as their name suggests, mine tunnels within leaf tissues of the cannabis plant. They essentially munch on the soft leaf tissue of your plant, but leaf miner isn’t a single species of pest. Many pests that are in the larval stage are considered leaf miners when they attack a plant and start chewing their way through the leaves. 

And unlike other pests that chew their way through the leaves or stems, like caterpillars, leaf miners are rather selective. They only target the soft tissue within the leaves. Doing so not only feeds them but the tunnels they build within the leaves also act as a safe haven against other predators. 

While this tactic is quite effective for larvae, it can wreak havoc on your cannabis plant. They can eat away major portions of the leaves, hampering their ability to conduct photosynthesis, which can lead to various growth problems for your cannabis plant. 

Leaf Miner Life Cycle

Leaf miners begin as eggs that are deposited by female insects. Once the eggs hatch, the emerging larvae start chewing their way through the leaves to fill their bellies and protect themselves from other predators. If they survive the harsh conditions, they morph into pupae and later turn into an adult. 

Leaf miner waves are a result of wasps, moths, or beetles mating, and while these species of insects are crucial for the ecosystem, it is also essential that their reproductive cycle is disrupted in your cannabis grow room to prevent a leaf miner invasion. 

How Do Leaf Miners Damage Cannabis Plants?

Leaf miners are easy to spot — their tunnels look like white brushstrokes across the leaves’ surface with spirals, twists, and turns. At first glance, these trails may look like parasitic worms, but they are not — they are a tell-tale sign of leaf miners. Here are some other signs of leaf miners on cannabis:

Winding Tunnels

One of the key indications of leaf miner damage is the existence of winding tunnels on the leaves. Usually, the larvae of leaf miners start burrowing the tissues of the plants, thereby creating tunnels in the process as they feed. Typically, these tunnels appear like slim winding lines that comply with the veins of the leaves. You’ll also see that the tunnels look translucent or white, depending on the type of leaf miner affecting the plant. 

Patches or Blotches 

Leaf miners produce uneven spots or patches on marijuana leaves as they feed. These areas typically show up lighter in contrast to the healthy tissues around them. The spots can differ in shape and size, varying from little areas to bigger blotches. The level of the damage depends upon the intensity of their feeding. 

Discolored Spots

Leaf miner larvae feed by sucking the internal layers of the leaf cells, which can lead to the formation of spots that are either discolored or transparent. It almost looks like these spots have little or no tissue at all. As they continue feeding, these spots might transform from yellow to brown spots, indicating severe damage. 

Distortion

Leaf miner feeding can cause curling or distortion. As the larvae eat through the tissues, the leaves can curl inward and look distorted. Sometimes, when the infestation is too severe, the curling may vary from the edges of the leaves rolling to significant deformations of the leaves. 

Stunted Growth

Severe leaf miner infestations can negatively impact the overall growth of your cannabis plants. The damage caused by leaf miners disrupts the normal functioning of the leaves and also affects the plant's ability to carry out photosynthesis and absorb nutrients efficiently. This can result in stunted growth, reduced vigor, and diminished overall plant health.

Premature Leaf Drop

Prolonged and extremely severe leaf miner infestations can cause affected leaves to prematurely drop from the plant. The damage caused by the larvae weakens the leaves, making them more prone to detachment. This can lead to a loss of foliage and further compromise the plant's ability to photosynthesize and produce energy.

Presence of Adult Flies

Adult leaf miners are typically small in size. They sport metallic or dark-colored bodies. You’ll notice that they are generally present around plants that are infested. These flies are the adults that emerge from pupae that develop inside the leaf tissue

In short, these are the indications you should look for:

• Yellow or white lines on the leaves
• Pale blotches on the top side of the leaves
• Leaves turning brown
• Leaves falling prematurely 
• Stunted plant growth
• Rolled or distorted leaves

But what makes leaf miners so dangerous for your cannabis plant aren’t the trails but what those trails do to the plant. Leaf miners can hamper the plant’s ability to generate energy. So, if your cannabis plant suffers from leaf miner damage, it may not grow as quickly as you’d expect and will eventually stop growing at all. Even the yield can be affected if the problem isn’t addressed on time. 

How Can Leaf Miners Affect the Yields of Cannabis Plants?

Reduced Photosynthetic Ability

Since leaf miners create tunnels when feeding on the leaves, it can influence the plant's photosynthetic ability. Plants rely on photosynthesis to capture sunlight and produce their own food. When this process is affected, the plants grow slower, don’t absorb nutrients well, and produce less yield. Also, since leaf miners cause the leaves to drop prematurely from the plant, the plant has fewer leaves to conduct photosynthesis, thereby damaging and weakening the plant further. 

Nutrient Deficiencies

Leaf miners not only physically damage the leaf tissue but also disrupt the plant's ability to absorb and transport nutrients. As they feed on the inner layers of the leaves, leaf miners can remove or damage the cells that are responsible for absorbing nutrients. This disruption can lead to nutrient deficiencies, where the plant lacks essential elements necessary for healthy growth and development. Nutrient deficiencies can negatively impact the plant's ability to produce robust buds and result in reduced yields.

Weak Structure

Severe or long-term lead miner infestations can damage and weaken the structure of marijuana plants. As the larvae tunnel through the leaves, they can disrupt the structural integrity of the affected leaves and nearby tissues. This makes the leaves more prone to breakage or may eventually drop from the plant. The loss of leaves and compromised plant structure can impact the plant's ability to support the weight of developing buds, potentially leading to smaller yields.

Infections and diseases 

Thanks to the damage from leaf miners, other pests find it easy to attack the plant too. The tunnels these leaf miners create are perfect as entry points for other pathogens and diseases including fungi and bacteria that can wreak havoc on the plant. These full-blown attacks further damage the plant and impact its ability to produce good yields. 

How to Treat a Leaf Miner Invasion on Cannabis?

Leaf miner invasion is perhaps the easiest pest infestation to spot on cannabis, and once you have spotted them, it’s time to get moving before they cause further damage to your plant. 

As a cannabis grower, you have several options to choose from to get rid of leaf miners on cannabis, including chemical pesticides, but let’s not resort to that just yet. Here are some safe methods to get rid of leaf miners on cannabis.

Neem Oil

Neem oil is perhaps the best remedy to deal with several pests, including leaf miners. It’s produced from pressed seeds and fruits of the neem tree, and it is quite effective at killing and driving away pests. The best benefit of neem oil is that it is completely harmless to the plant and the environment. 

To use neem oil, mix a teaspoon of this oil in a liter of water. You can also add a few drops of surfactant to act as an emulsifier. Shake the solution well and use it as a foliar spray on your entire plant. This solution is best used during the vegetative stage, but avoid using it on a blooming cannabis plant as the pungent odor of the oil can hamper the buds’ flavor and aroma profiles. 

Spinosad

Spinosad is another organic and harmless product that you can use to kill leaf miners on your cannabis plant. These products can be used as a foliar spray — it will kill the pests on contact. It affects the nervous system of the pest, which kills them instantly. But remember, spinosad is safe for your plant, yourself, and your pests, it is still not the best product to use so it is not recommended for commercial growers. 

Beneficial Insects

There’s a reason leaf miners evolved to dig through the leaves to protect themselves — other pests love preying on these little bugs. So, you can use this to your advantage by introducing predatory insects into your cannabis garden. These beneficial predators will hunt down leaf miners and eliminate them over time. 

The parasitic wasp is your best friend here. This predatory insect is most effective at killing leaf miners; they patrol the garden, and once they spot a leaf miner, they puncture them with their sting, which paralyzes them instantly. Once the leaf miners are immobilized, the wasps lay their eggs on them, and the emerging larvae feed on the remains of the leaf miners. 

Sticky Traps 

Sticky traps are also an effective solution to eliminate leaf miners in their adult stage. Simply place these traps around your plant and adult leaf miners will make their way to these brightly-colored traps and get stuck on them. This is only effective for a minor invasion, but it is still worth using as a preventative measure. 

Pick Them Manually

If the leaf miner invasion on your cannabis plant is not so severe and of low population, you can also pick these little pests manually and eliminate them. Find the head of the trail and simply squash the pest with your nails. If you want to take this a step further, simply cut off any infected leaves since leaf miners can’t escape until they are done feeding on the leaves. 

How to Prevent Leaf Miners on Cannabis?

Preventing leaf miners from invading your cannabis plant is always better than dealing with them when they are already digging freeways inside your plant’s leaves. Preventing them will save time and effort while allowing your plant to grow in peace. Here are some ways you can prevent leaf miners on cannabis plants.

Identify the Infestation

Before you proceed with any kind of treatment, you must first be sure that you’ve identified leaf miners. Check the leaves well for any signs of leaf miner damage, including winding tunnels or blotches on the leaves. You may also see small yellowish eggs or larvae, and adult flies in the vicinity of the plants. Proper identification ensures that you are targeting the correct pest and employing the appropriate treatment strategies.

Remove Infested Leaves

Once you have identified infested leaves, you can start with the treatment. The easiest way to do so is by removing any leaves that are infected already. By removing these leaves, you’re eliminating their source of food, thereby ensuring that they don’t continue affecting the plants. This means that they can’t reproduce anymore either. Use clean pruning shears or scissors to carefully cut off the infested leaves, so you don't damage the healthy parts of the plant. Place the removed leaves in a sealed plastic bag to prevent the leaf miners from spreading and dispose of them in the trash.

Cover Your Plants

One effective way of preventing leaf miners from invading your cannabis plant is to cover your plant with mesh row covers that protect your plant from pests while allowing adequate light and airflow to reach the canopy. They work well for both indoor and outdoor plants and the mesh is small enough to block moths and flies. Just remember to inspect the mesh regularly as they are easy to tear due to strong wings. 

Observe Your Plant Often

Next, regularly observe your plant to look for any signs of leaf miner invasions. Check for any symptoms or signs of deficiencies, lines on the leaves, presence of other insects around the canopy, etc. Look for small winding tunnels or blotches on the surface of the leaves, and the presence of small, yellowish eggs or larvae. Early identification allows for prompt action and prevents the infestation from spreading further. If you find even a minor sign of leaf miners, prune the effective leaf immediately to eliminate the problem before it becomes serious.

Monitor and Repeat Treatments if Necessary

After you treat the plants, monitor them closely for any signs of continued leaf miner activity. If you observe new leaf miner activity, you should repeat the treatment process or employ alternative control methods if your original treatment wasn’t effective. Continuous monitoring is crucial to detect any resurgence of leaf miners and take appropriate action promptly to prevent further damage. 

By implementing various preventive measures such as companion planting, where you grow plants that naturally repel leaf miners or attract beneficial insects, you can rest assured that your plants will be left alone. Utilize sticky traps, spray your plants with insecticidal soap and water often (avoid the buds), and make sure you feed the plants appropriately. Take care of your plants by checking the pH, watering them when needed, and providing air circulation, you’re already ahead of the problem. Healthy plants are more resistant to pests and can recover better from infestations.

Keep Your Grow Room Clean

Always keep your grow room clean of debris and dead plant matter. Such materials attract pests to your garden and no matter the defense mechanisms, your plant will face many pest invasions if the grow room is not clean and sanitized. So, always keep your grow room clean, sanitized, and free of any dead plant matter. 

Crop Rotation

If you’re growing outdoors, avoid planting cannabis in the same location every year. This is because leaf miners and other pests may overwinter in the soil or nearby debris, so rotating your crops disrupts their life cycle. By changing the planting location, you automatically decrease the chances of leaf miners finding and infesting your cannabis plants.

Summary: How to Get Rid of Leaf Miners on Cannabis?

Leaf miners are creative little creatures — these larval-stage pests dig through the leaves of your precious plant to feed themselves and protect themselves from other predatory pests. But in doing so, they eat away the crucial tissues of your plant’s leaves, hampering your plant’s ability to produce energy and sustain itself. 

You can spot leaf miners on your cannabis plant thanks to the white lines that form due to their tunneling, and if you don’t address the issue on time, your plant can eventually stop growing entirely and suffer from a lack of energy. 

So, if your plant is suffering from a leaf miner invasion, use neem oil, spinosad, sticky traps, or your fingernails to get rid of them as soon as possible. You can even use parasitic wasps to eliminate them. And then, use other preventative measures as mentioned above to stop them from making their way to your cannabis plant ever again.