Want to know how to get rid of leafminers?
You aren’t alone.
These tiny pests aggravate millions of gardeners each year, and when they continue to rear their ugly heads in your garden, it can be incredibly disheartening.
You don't need to lose hope quite yet, though.
There are plenty of ways you can get rid of leafminers with a bit of practice - and a whole lot of patience.
Before we share our best prevention tips and eradication methods with you, let's cover some general information on this pest, along with how to identify it.
What Are Leafminers?
Leafminers are small pests that chew and tunnel holes in your plants’ leaves. They create a web of destruction that is not only hard to reverse but also highly distinctive.
These pests are bugs of many names, known by monikers such as tomato leafminer, citrus leafminer, spinach leafminer, and more.
Of course, the kind of leafminer you are dealing with is likely dependent on the kind of plant they are causing problems with.
There are several types of leafminers, but for the most part, they also produce disastrous effects in your garden.
These bugs usually appear as nondescript black bugs. It’s not actually the adult version of the pests that damage your plants, but instead, their larvae.
Most leafminers are actually from the sawfly, fly, or moth families, although there are some exceptions to this.
Adult leafminers lay their eggs on a leaf’s surface. Just one female can lay more than 200 eggs, with the eggs maturing into larvae in less than ten days.
The larval stage is when leafminers are the most destructive - they will feed for three weeks in this stage.
Leafminers are found all over the world and are known to feast on all kinds of plants, including most trees, ornamental plants, shrubs, and edible crops.
Signs of Leafminer Infestation
Leafminer damage isn’t pretty - and left unaddressed, it can result in serious problems for your plants.
If you notice any of these signs of leafminer infestation, take immediate reaction to resolve it.
The most obvious sign of an infestation is yellow lines in your leaves. These look like small squiggles. The lines signify that the leafminers have bored their way through the leaves.
Although the damage usually takes the form of squiggles, it can appear as blotches and spots, too. Leafminers can cause portions of crops or entire crops to become unsafe to consume.
They can open up the door for fungal or bacterial growth on the leaves, which is not only unappealing, but can also be deadly to the plants.
How to Prevent Leafminers
We have some methods and products that will get rid of leafminers quickly if needed. But, we should start by sharing some advice on how you can prevent these pests altogether.
Rotate Your Crops
One of the easiest ways to prevent leafminers, at least in subsequent growing seasons, is to rotate your crops. These pests can overwinter in the soil.
Once the weather warms, the leafminers will emerge from the soil and begin wreaking havoc on your crops once more.
Rotate your crops each season (and ideally don’t plant the same species in the same spot for more than one year) to reduce the temptation for these pests to feed on your plants.
Rotating your plants is a good garden practice in general, and won't just prevent leafminers, but most pests and diseases.
Know Your Plants & Monitor For Changes
Familiarize yourself, to the greatest extent possible, of what’s normal for your plants and what is not.
Some leafminers are incredibly selective, feeding only on one kind of plant. All of the juicy tissues of leaves tend to be vulnerable to damage, but these pests do prefer leaf parts that have less cellulose. They tend to prefer soft, sweet plant tissues.
Keep your plants healthy, as those that are growing strong and vigorously are the least likely to be damaged by these pests.
Feed them regularly with plant nutrients and ensure they have everything they need to grow to the best of their ability in terms of nutrition, lighting, environmental conditions, etc.
Use Floating Row Covers
Floating row covers can not only help keep leafminers off your plants, but they can prevent other kinds of pests, too.
The theory behind floating row covers is simple - if the pests can’t reach your plants, they can’t inflict any damage!
You will put floating row covers over any vulnerable plants. The leafminers won’t be able to get to the leaves.
Just make sure you remove the covers of any plants that need to be pollinated when they are flowering so that bees and other pollinators have access.
Thoroughly Check Your Transplants
If you’re transplanting new plants into your garden, check them thoroughly, paying close attention to the leaves. If you see any leafminers, remove the leaves.
You can also return the plant to the nursery for a refund in most cases. Try to get into the habit of checking your plants before you purchase them to make sure there are no signs of pests or diseases.
By quarantining new arrivals to your garden for a week or two, you can prevent passing on pests or diseases to your already established plants.
Grow a Trap Crop
Trap crops are used to keep leafminers out of your valuable plants. These plants are meant to be more attractive to a pest and are usually planted nearby so the leafminers infest that crop instead of your other plants.
Some good options include lambsquarter, velvetleaf, and columbine.
Try Sticky Traps
Yellow sticky traps are meant to be hung on or near plants that are either experiencing or are vulnerable to leafminer damage. These can be used to get rid of leafminers as well, but definitely do better as preventative care.
They aren’t as effective for larvae, but can trap adult moths and flies that want to lay their eggs on your plant leaves. Once the adults get stuck in the traps, they’ll die off.
You can also try pheromone traps, which work in a similar fashion but draw pests in with their scent instead.
These are only effective for certain kinds of leafminers, like citrus leafminers.
How to Get Rid of Leafminers
Even if you put in the effort to prevent leafminers, you still may struggle with them.
This is especially true if your are growing outdoors, as there isn't much stopping them from sniffing out your garden.
We are now going to teach you how to get rid of leafminers if they do arise. We'll start with quick fixes for small infestations, and work our way towards more invasive methods such as pesticides.
Pinch Them Off
If you notice the telltale trails of leafminer damage on your plants, one of the easiest ways to stop these pests in their tracks is to physically remove them.
Pinch along the trails, using your forefinger and thumb. If there are any leafminers inside the leaf, this should kill them.
If you notice a leafminer infestation, it might be beneficial for you to remove all of the infected leaves, too.
When you dispose of them, don’t compost them, especially if the compost is close to your garden.
There is no guarantee that the eggs and larvae will die off before the next growing season, when you use the compost in your garden. Instead, put the leaves in your garbage can.
Use Beneficial Insects
One of the easiest and most ecologically friendly ways to get rid of leafminers is to introduce beneficial insects.
There are all kinds of insects that feed upon leafminers, including predatory wasps like Diglyphus isaea.
You can buy these insects from online nurseries and then release them into your garden.
You can also attract these insects to your garden by planting predator-friendly plants, such as yarrow and dill.
One particularly effective species of wasp is the leafminer parasite, or Diglyphus isaea.
This wasp is able to find larvae when they are deep inside their trails within the leaves. They will lay eggs inside the larvae of leafminers. Once the eggs hatch, the wasps consume the larvae from within.
Use Diatomaceous Earth Sparingly
Some gardeners use diatomaceous earth to combat leafminers. It can work, but only to a limited extent.
Powders such as diatomaceous earth just aren’t as effective at getting rid of leafminers because leafminer larvae don’t come into direct contact with them as often.
The best way to use a powder like this - which is non-toxic and safe to use in an organic garden - is to spread it dryover the surface of the soil beneath a plant. You can also dust it on the surfaces of the leaves.
Try Neem Oil
Neem oil is another natural treatment that is highly effective at getting rid of leafminers. Neem oil is made from a plant and helps to halt the life cycle of a leafminer.
It reduces the number of larvae that later become adults, thereby reducing the eggs that the adults can then lay.
You won’t notice immediate results when you use neem oil, but with a bit of patience, you’ll find that this treatment can really make a difference.
Get Rid Of Leafminers With A Pesticide
For the most severe infestations, you are best off using a pesticide to get rid of leafminers.
It’s only recommended for a severe leafminer outbreak that has not responded to other treatments.
Look for products containing Spinosad or Bacillus Thuringiensis. BT is one of the most effective compounds for combatting leafminers.
It can be applied to the leaves of your plants. Since it’s a naturally occurring bacteria, you don’t have to worry about it contaminating your crops or having any toxic effects, either.
Here are some products we recommend for getting rid of leafminers in the garden:
- Bonide Captain Jack's Deadbug Brew Concentrate
- General Hydroponics AzaMax Concentrate (OMRI Listed)
- Monterey Lawn & Garden Insect Spray with Spinosad (OMRI Listed)
- Blacksmith BioScience Armory Beneficial Bacillus
Get Rid of Leafminers With a Bit of Patience and Skill
A leafminer infestation isn’t the end of the world, but it can certainly be aggravating to deal with.
Nobody wants to see those telltale tunnels on their salad greens! However, now that you know the best ways to get rid of leafminers, you’ll be on the right track to eliminating these menaces for good.
If you want to learn more about keeping your grow room free of issues, check out our complete guide on the most common grow room pests & diseases.