If you make a living selling plants, the discovery of leaf miner activity can be devastating. If you’ve found their signature tunnels on your plants’ leaves, you’re probably wondering how exactly they got there and what you can do about it.
Leaf miners are the larval stage of a variety of flies, beetles, and moths. To get rid of leaf miners, you can use beneficial bugs or floating row covers. There are also many sprays available that will drive these pests away from your garden.
Many people are unfamiliar with leaf miners and the best ways to get rid of them. We hope that this post answers all your leaf miner questions!
What are Leaf Miners?
Leaf miner is an umbrella term covering any larvae that eats plant leaves.
The larvae usually appear as worm-like maggots, about 1 – 2 millimeters in length. They may be white, pale yellow, or green, but you’re more likely to notice the adults than the larvae. You might notice small black or gray flies, beetles, or moths around your plants. This, along with the tell-tale leaf pattern damage they cause, indicates the presence of leaf miners.
Adult female flies or beetles lay their eggs either inside or underneath plant leaves. Once these eggs hatch, the larvae tunnel into the leaves and create long, squiggly lines, or “mines” as they feed on the soft inner plant tissue. Although some types of leaf miners are more likely to target specific plants than others, a wide variety of plants are susceptible to leaf miner damage.
Which Plants do Leaf Miners Attack?
There is an extensive range of plants that leaf miners may use as their hosts. Some types feed on ornamental plants, while others feed on trees. Many also feed on fruit and vegetable plants, including:
- Beans
- Peppers
- Spinach
- Blackberries
- Lettuce
- Citrus fruits
- Cabbage
These pests are prevalent and often found in home gardens, landscaped areas such as backyards, and greenhouses. In addition to edible plants, leaf miners tend to feed on trees, shrubs, and ornamental flowers such as lilacs. Because there is such a wide range of plants that can be affected, it’s essential to know what to look for and understand what leaf miners can do to your plants.
Will Leaf Miners Kill Your Plants?
Typically, leaf miners will not cause anything but aesthetic damage to your plants. However, some plants are more susceptible to damage than others, and certain types of leaf miners can cause more damage than others.
The damage caused by leaf miners will usually appear as yellow or brown squiggly lines throughout the infected leaves, but may also appear as spots, blotches, or mottling. This will make them look unattractive and reduce the value of your plants, but the damage isn’t usually life-threatening unless it’s severe.
Sometimes, the trails left behind by leaf miners can pave the way for future fungal or bacterial infections. Pathogenic fungi and bacteria can sometimes find their way into the mines left behind from eradicated insects, causing the leaves to yellow, die, and fall off. While this usually won’t be a health problem for plants, it can make them look less aesthetically pleasing or reduce your crop yield.
As you may expect, younger and smaller plants are more susceptible to severe damage from leaf miners. Strong, healthy plants, on the other hand, can usually tolerate them. If you’ve had leaf miner damage in the past, you can help prevent recurrence by regularly fertilizing, pruning, and using high-quality soil.
What do Leaf Miners Turn Into?
There are many different species of leaf miners, so they may turn into flies, beetles, or moths, depending on which insects they are. Some of the most common leaf miners in the U.S. include:
- Jewel beetles
- Weevils
- Leaf beetles
- Sawflies
- Moths
Depending on the exact species you have, you may experience more plant damage than you’d expect. Weevils, for example, can cause severe damage to plants as adults.
Another type of highly damaging leaf miner is the horse chestnut leaf miner. As adults, these moths feed on plant tissue. The leaves affected by the burrowing larvae can also stunt the plant’s growth, and this damage often spreads across the entire tree. The leaves will brown, and even when new leaves grow, they will still be affected by the damage.
Can You See Leaf Miners with the Naked Eye?
Usually, leaf miner larvae aren’t visible to the naked eye. They’re tiny, and since they burrow inside the leaves, it’s usually easier to identify their presence from the mines themselves.
While you may not be able to see the leaf miner larvae, you’ll usually be able to see the adult flies, beetles, or moths. If you’re really interested in seeing the larvae, you can try placing an infected leaf under a microscope. You may also be able to see the eggs before they hatch by looking underneath your plants’ leaves.
How Long do Leaf Miners Live?
Throughout the year, a leaf miner infestation can go through several different generations. Each generation will take approximately 30-40 days to emerge as flies, and the pupae can survive through the winter.
Adult flies typically emerge during late spring, usually around April or May. The larvae themselves are active inside the leaves, feeding on the plant tissue for about two to three weeks. They then drop to the ground and transform into pupae, where they stay until they grow into adult flies.
7 Ways to Kill Leaf Miners
When you’re dealing with leaf miners, natural solutions always work best. Because the larvae burrow inside of the leaves, they are protected from insecticidal sprays for most of their lives. For this reason, natural methods are often best at limiting the damage caused by leaf miner larvae.
Natural Methods
Here are some of the best natural methods for dealing with a leaf miner infestation:
Introduce Beneficial Bugs
If you’re dealing with a leaf miner infestation in an outdoor environment, introducing some beneficial bugs to the area is a great way to let nature deal with the problem. One of the best bugs to look into is a type of wasp called “diglyphus isaea,” or the leaf miner parasite. As the name suggests, these wasps are natural enemies of leaf miners.
You can find leafminer parasites at some nurseries. They find leaf miner larvae inside of the trails they make and start by stinging them. This paralyzes the larvae, which stops them from tunneling in their tracks. After they sting the leaf miners, they’ll lay eggs inside the larvae, killing them and stopping the reproductive cycle.
You can also try applying a nematode spray to the foliage. They’ll enter the tunnels through exit holes made by adult leaf miners or feeding punctures and then enter the larvaes’ bodies and release symbiotic bacteria into their blood. This kills the leaf miners, usually within just 48 hours. If you add nematodes to the soil of your plants, it may even help eliminate adults as well!
Try Floating Row Covers
Floating row covers are woven or spun-bonded covers, typically made of either a plastic or polyester material, that can be placed over plants. They still allow water, light, and air to enter the area but keep pests, including leaf miners, from entering.
It’s best to place floating row covers on your plants as soon as you plant them. However, if you can’t do this, it’s essential to make sure you don’t close off an area that already has an infestation. If you do this, there will be no way for the existing pests to be driven away. Floating row covers will also have to be removed during pollination if you’re working with plants that need to be pollinated by bees or other insects.
Not only will these coverings prevent adult females from landing on the plants to lay their eggs, but they’ll also prevent larvae from dropping to the ground and burrowing into the soil. This disrupts their natural life cycle and is especially effective when combining them with other pest control methods.
Consider Adding Trap Crops
Just like people and animals, leaf miners prefer some types of food over others. If their favorite plants aren’t available, they’ll be happy to burrow into anything available, which could put your most important crops in danger. To keep your plants safe, you can try planting “trap crops,” or plants that are more attractive to leaf miners, around the perimeter of the plants that you’re trying to protect.
Trap crops will entice leaf miners to move away from your important plants. Some of the best trap crops to use include Columbine, Lambsquarter, and Velvetleaf, as leaf miners tend to prefer these over others. Plant them close to the affected plants in your garden to drive them elsewhere.
Use Brightly-Colored Sticky Traps
Sticky traps work just like the flypaper you might use for ants or house flies. Leaf miners will be attracted to sticky traps, get stuck, and be unable to disrupt your plants further. Insects are attracted to the bright colors that many traps come in, especially those that are yellow and blue. Consider adding some to your garden to prevent leaf miners from coming in contact with your precious plants.
Regularly Prune Your Plants
Checking for infected leaves and regularly pruning your plants is one of the easiest and most effective ways of disrupting the leaf miner life cycle. Inspect the leaves on your plants regularly, checking for any signs of active larvae. If you see any tunnels, simply cut off and discard the leaves.
To be sure the larvae won’t survive the pruning, you can also try squeezing the infected leaves at the tunnel site with two fingers to crush any active larvae. If the outbreak is caught soon enough, pruning should be enough to resolve the issue.
Will BT (Bacillus Thuringiensis) Kill Leaf Miners?
In most cases, BT will be able to help with a leaf miner issue. It’s available in both a powder and spray and will poison the larvae if they come in contact with it. For best results, use the BT spray to coat the entire plant, paying particular attention to the leaves to ensure it penetrates the inside. Make sure to spray at the first sign of tunneling to ensure it reaches the larvae before they mature into pupae.
Other Ways to Kill Leaf Miners
If the above measures don’t work, you can try using fast-acting natural insecticides to rid your plants of leaf miner activity. Using a natural insecticide is much better than using a synthetic variety, especially in the case of edible plants like fruits, vegetables, and herbs, because it contains no harmful ingredients. They’re derived from natural ingredients, like other plants that contain insecticidal properties. It’s always best to go natural when you’re working with chemicals like these!
If you’re using one of these products, you’ll need to be sure that you’re spraying your plants at the correct time to disrupt the leaf miner life cycle. Some pesticides are specifically meant to target leaf miners. If you use one of these, you can spray your plants with them at any time, and they’ll still work effectively.
What Can You Spray to Kill Leaf Miners?
You can buy or make a few different natural sprays at home to kill leaf miners and save your plants. When using spray remedies, it’s important to remember to spray at the correct time. Spraying too early or too late won’t allow the insecticide to reach the larvae in time to kill them before they mature into flies and repeat the cycle.
Here’s a foolproof way to be sure that you’re spraying at just the right time: in the early spring season, around March or early April, place a few leaves that show signs of tunneling into a Ziplock bag. Check the bag every day. When you start to see small black flies, moths, or beetles in the bag, indicating the larvae becoming adults, spray the whole plant generously each day for a week. Below are a few effective natural sprays you can use to kill leaf miners.
Neem Oil
Neem oil works by slowly suffocating leaf miners and is one of the most commonly known ways to get rid of them. The larvae won’t be able to feed, and the adults won’t be able to fly or mate. This both reduces the number of larvae that turn into adults and the number of eggs that will be laid for the next generation. It’s not a quick way to kill leaf miners and may not eradicate the entire population, but it will affect them enough to make them move on to another plant.
As an added benefit, neem oil will also fertilize your plants! However, since it is an oil, there is a greater risk of burning. To avoid burning your plants, avoid using any other sulfur-based fungicides within a week of spraying the neem oil. Always make sure to coat the entire surface of the affected plant, paying particular attention to the leaves, and spray according to the directions on the bottle.
White Oil
White oil works in the same way that neem oil does and can be made with ingredients you probably already have at home. To make white oil, you’ll need:
- A 16 oz spray bottle
- 1 tsp of vegetable oil
- 1 tsp of dish soap
- Enough water to fill the bottle
Begin by mixing the oil and soap in the bottle. Then add enough water to fill the bottle and shake until well-mixed. You’ll only need to spray a light coating on your plant, but make sure each leaf is fully coated on both the top and bottom to rid them of pest activity.
Castille Soap
If you have any Castille soap laying around the house, you can try mixing 1 tsp with 15-20 oz of water and spraying it on your plants to get rid of leaf miners. You’ll want to spray it on both the front and back of each leaf and any other foliage on your plants. It’s not as effective as neem and white oil, so you’ll need to spray multiple times for it to be effective.
Will Ladybugs Kill Leaf Miners?
In most cases, ladybugs can be an effective measure against leaf miners. Ladybugs usually prefer to eat pests like aphids but will still eat the leaf miner larvae if nothing else is available! Like wasps and nematodes, they are beneficial bugs. The advantage of using ladybugs is that, when you have the right species, they’re not harmful to people, pets, or plants.
There are many different species of ladybugs, and it’s crucial to remember that not all types are beneficial. For example, a common species called Epilachninae are known to feed on plants and should not be used as pest control. The Hippodamia convergen, on the other hand, is a natural larva predator and should take care of your leaf miner problem.
Will Sevin Dust Kill Leaf Miners?
Unfortunately, Sevin Dust will not be an effective measure against a leaf miner outbreak. While it can kill most types of insects that live on plants or in the soil, Sevin Dust won’t be able to penetrate through the leaves to the inside where the larvae tunnel and feed.
Sevin Dust won’t be enough to rid your plants of adult leaf miners, either. They don’t feed on the plant; they just land on the leaves momentarily to lay their eggs. Because of this, they likely won’t come in contact with the plant enough for the material to kill them. Even if they do, the eggs will likely have already been laid before the dust takes effect. To get rid of leaf miners, you’ll have to use something else!
Are Leaf Miners Safe if You Accidentally Eat Them?
Accidentally consuming a leaf infected by leaf miner activity won’t pose any harm to people or animals. They’re not parasitic or poisonous, so while it may not be pleasant to learn that you’ve just ingested leaf miner larvae, it won’t do you any harm!
Leaf miners are known to be big fans of leafy vegetables like spinach and chard. If you notice a leaf with visible tunnels, it’s best to throw it away. However, you won’t be in any danger if you do accidentally eat one of these leaves.
Closing Thoughts
Leaf miners pose much more of an aesthetic risk to your plants than a health risk, but they’re still not pleasant to deal with. Thankfully, there are many ways to drive these pests away from your plants so that the cycle does not continue in the future.
Here are Some of my Favorite Gardening Products and Tools
Thank you for reading this article. I hope you found it helpful for growing some new plants in your home or garden. Here are some products I like that I hope you’ll also find helpful. These are affiliate links, and I am compensated for referring traffic. But in all honesty, these are the exact product that I use or recommend to everyone.
Soil: For high-quality soil, I really like Fox Farm Ocean Forest. I do all my growing in containers and this soil has worked great for me. I like how they use nutrient-rich contents like earthworm castings, bat guano, and composted crab and fish.
Fertilizer: Currently I am using a seaweed-based organic fertilizer call Neptunes Harvest. This is a great milder fertilizer option if you want to use something organic. If you want a more powerful fertilizer, I recommend Fox Farm Liquid Nutrient Trio, lots of people have had great growing success with this product.
Pruning Shears: Pruning shears are one of the most useful gardening tools to have because it’s important to prune your plants to keep them healthy. The pruning shears I recommend are the Gonicc 8’’ pruning shears. I like them because they are built sturdy and work both on bigger and smaller plants, so you don’t need to have multiple pruning shears.
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