Leaf Miner Invasion? How To Eliminate Trailblazing Larvae

Ed Wike
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Leaf Miner Overview

The process of leaf mining is more common than you might think. Almost all leaves on the tree or garden in some form or another have a leaf miner.

There are over 300 species of leaf miners on over 50 families of trees. Even the rarest tree in your garden seems to have something devouring it.

Ancient Greeks wrote about it, Shakespeare about it, 19th century writer Darwin on it, and it's still going strong today.

What is it? A tiny worm that eats the tissue in between the leaf layers, the phloem and the surface of the leaf. This leaves the outside of the leaf looking like lace and the inside looking like Swiss cheese.

Although not visible, the worm (living in the leaf) can hop onto another leaf and continue to the leaf isn’t entirely eaten.

The damage is only indirect: the leaf is no longer photosynthesizing, the leaves start to fall off and the tree loses its ability to grow.

The effect of leaf mining on the tree is dramatic. If no action is taken, it will likely die.

The first and easiest fix is to curb all contact, from the tree, with the leafminers. The best way to do this is by keeping your tree trimmed. The problem with this method is that it removes the leaves now, and later when that leaf falls off, it will come back to visit.

All About Leaf Miners

The leaf miner is a serious indoor and foliage pest that worms its way on the life cycle. Exploiting a leaf or a bud to live for itself, it will create a passage to feed and transform into a pupa.

These creatures start their reproduction after the first warm days of Spring and they target all sorts of vegetables, from the common spinach to ornamental plants. In order to ensure the best of your food, we recommend you follow these 4 simple steps:

Prepare It, Spray It, Spray it Again – Make sure you use a decent pesticide formulated for leaf miners. We would recommend asking an expert in the nearest garden center for a professional advice.

Control The Source – Check your plants for the presence of insects and remove them if possible. There are many different types of leaf miners, with specific modes of action and specific chemicals to kill them.

Find The Eggs – Inspect the underside of the leaves and look for the eggs. This is usually the first sign of a leaf miner infestation.

Remove The Eggs – Use scissors to cut along the underside of the leaves where you have found the egg sacs and destroy them. This will prevent the insects from depositing more eggs in your plants.

The leaf miner is a pest that you can easily spot if you have a bit of knowledge. Make sure you address the problem as soon as possible, in order to prevent a widespread assault.

Leaf Miner Life Cycle

Leaft miners are most active in the spring and can become a severe problem on the leaves of your plants and trees. These leaf eating larvae have a predetermined life cycle, and can be stopped before they wreak havoc on your garden.

A leaf miner infestation starts with the Leaf Miner Female lays her eggs on the leaf. After the eggs hatch, the larvae mine straight down through the leaf, exposing a clear trail. You will often see small black larvae doing what looks like moving windows on the leaves. Cutting the leaf open will expose the larvae to damage and likely death. The larvae will then molt (shed) their exoskeleton, and continue to make their way through the leaf until they finish the leaf especially noticeable on your trees in their spring or fall. As with a few other garden insects such as Aphids, you can often spot leaf miners in the garden by the hundreds as they cluster together on a single leaf.

If you use good garden management practices like chemical-free pest control, you may be able to minimize leaf miners without having to resort to chemicals.

Common Habitats Of Leaf Miners

It is rare to find the infestation of leaf miners before they launch their trailblazing invasion. What you can usually find are the damage and signs of their presence. The most common locations for leaf miners to set up camp in are:

  • Ivy leaves
  • Evergreen holly leaves
  • Gardenia leaves
  • Jasmine leaves
  • Tulip leaves
  • Juniper leaves
  • Privet leaves
  • Virginia Creeper leaves

It can seem like your entire tree is being eaten by a leaf miner swarm. The difference between infestation and a leaf miner outbreak is leaf miners attack leaves on a mass scale.

Leaf miner damage is difficult to control due to their mobility. They carefully work their way down one leaf and then hop to a new leaf. This process is repeated until they've mined the leaf to death. You rarely find them attacking the same leaf from day to day.

What Do Leaf Miners Eat?

There aren’t many people that are enthralled by the idea of spending time with leaf mining flies, the larvae of the Agromyzidae family of flies. The flies lay eggs on plant material, usually on the under-side of leaves. They are commonly found between April and September. The eggs hatch into a crop of wriggly, white larvae that are very mobile and consume the leaf material from the inside-out.

These leaf-munchers cavort over the leaf material, eating as they go. They can tunnel through the whole leaf or “mine” in only certain parts, mainly the veins. They leave irregular brown patching behind as the leaf deteriorates. They often create serpentine mines throughout a leaf, leaving a lacy pattern on the leaf. The leaf can take on a lace-like appearance.

How To Get Rid Of Leaf Miners

One of the largest pests in the world, leaf miners can completely destroy an entire crop or garden. The most effective way to get rid of them is to rid your garden of the insects’ favorite food source … leaves! In order to do this you must understand what leaf miners eat. Then you may select the safest and most effective treatment for your particular host plant.

First you must understand what leafminers eat. They love to eat the soft tissue of leaves. In order to eliminate the leafminers you must cut off a leaf where the leafminer is located. This will prevent any more larvae from growing to adulthood. Don’t be concerned about killing the larvae yourself. The pupae stage is the most damaging one for this insect and will lead to your plant or fruit being demolished in no time.

A great way to prevent leafminers is by using row covers! Row covers allow the plants to grow uninterrupted and protect the fruit or vegetable. Any leafminers that fly in will not be able to have anything to eat and will go elsewhere.

If you are using row covers then safe soap is an effective way of removing the leaf miners if they are found to be inside of the leaves. Many people find that smearing the leaves with the insecticide achieves less results than covering the plants.

Organic Leaf Miner Control

Treat your plants with a weak neem oil solution, apply 2 to 3 times every 7 to 10 days.

Neem oil is a natural insecticide and miticide that is derived from the Neem tree, which is native to India and northern Africa. As it is a natural product, there are no chemical, petroleum, or gasoline derivatives in it.

Neem oil is just as effective in combating Leaf Miner infestations as synthetic chemical products. Neem oil is also considered a broad spectrum pesticide, as it contains insecticidal, fungicidal, nematicidal, and acaricidal properties.

For Leaf Miner flies, neem oil works by paralyzing the immature stages as well as their eggs, hence stopping both the growth and development of the larvae.

Set up yellow sticky traps in areas where you have a heavy infestation.

Sticky traps work by capturing male leafflies, which are attracted to yellow colored objects. Within seven days the trapped leafflies create an accumulation of up to 20 leafflies per wipe.

Set up yellow sticky traps in areas where you have a heavy infestation.

Sticky traps work by capturing male leafflies, which are attracted to yellow colored objects. Within seven days the trapped leafflies create an accumulation of up to 20 leafflies per wipe.

Written by Phyllis Patterson.

Environmental Leaf Miner Control

Environmental leaf miner control usually focuses on the habitat the larvae develop in. The larvae are only active in the summer months. They have a short development cycle, which is another reason to be vigilant only in summer months.

Their lifecycle is closely tied to the lifecycle of the plants. These insects release eggs into the soil around shrubs, trees, and other plants. The hatching takes place only when the soil temperature reaches approximately 70° F. Once hatched, the larvae burrow into the plant matter to eat the plant tissue. If conditions remain favorable, the larvae will develop into outdoor leaf miner adults and lay eggs on the prey to complete the cycle.

You can still leverage environmental leaf miner control methods even if mined plants are too far gone to stop the larvae. Identify the plant type and the affected areas. Nearby plants should be inspected as well for signs of leaf miner infestation.

Preventing Leaf Miners

When you first notice the conspicuously thin, pale trails across your plants’ leaves, you may be wondering if you have leaf miners, and if so, how to prevent them.

When leaf miners do show up, it is not uncommon to become angry and frustrated that these pests are destroying your crops. But the reality is that most of the situations in which you notice leaf miners, the small larvae are not the actual culprit. In many situations, the leaf miners are just the natural predators of a bigger danger.

Either way, leaf miners are a wiry threadworm type of a parasite that spend their larval stage eating the leaves of the plants they have invaded. The actual culprit – the one that has possibly infected your plants – is being carried by the beetles or moths whose larvae are the leaf miners.

If you notice an infestation of leaf miners, the first important step is to get rid of the adults. While it is likely that they will not be partaking in any actual leaf eating, they will be flying around, depositing their larvae onto different plants. This is why it is important to not confuse the adult beetles with being the problem.

The trick to dealing with leaf miners is to deal with the adults that carry them and to manage the plant hosts to prevent breeding.

Frequently Asked Questions

What are leaf miners?

Leaf miners are tiny caterpillars that live in the canopy of trees. They are the larvae of midges, mosquitoes, and flies that lay their eggs in the leaves of trees.

What is so bad about leaf miners?

Leaf miner larvae bores into the leaf tissue, often en mass, leaving a trail of muddy brown lines. Their trail also makes it difficult for the leaf to take in nutrients, water, and sunlight.

How do I get rid of leaf miners?

There are a variety of ways to eradicate leaf miners. The tree owner (you!) will have to decide what he or she wants to do about the situation. A certified arborist can help you determine the best plan of action for your tree. Methods vary depending on the location of the tree, the level of infestation, and the damage caused. Not all methods are easily applied by homeowners.

Who picks up the tab if the damage is severe?

Homeowners are not typically responsible if the infestation is the result of poor tree maintenance or insufficient care by an arborist.

Q: Will diatomaceous earth kill leaf miners?

Lawns with leaf miner infestation are often riddled with thin, brown lines that run across the grass blades. These lines, or mines, are cutting away the chlorophyll of the leaf blades. This causes grass to become lighter and thinner. It can also cause leaves to die and brown or yellow. Once the leaf blade looks thin and the grass starts turning yellow, the window for treatment is closing.

There are several ways to eliminate leaf miners in the lawn. One way is to eliminate impediments, such as poor drainage and areas of shade. Leaf miners thrive in these areas where they are protected from pesticides and the sun. If leaf miners are found, lawns that are less than a year old should be fertilized with compost. This compost encourages tiller growth to fill the gaps where leaf miners are attempting to mine.

Neem oil can be used to prevent leaf miners in other areas. Neem oil works by preventing larvae from forming adult moths in the leaves. If the larvae form into moths, they will live for only a short period of time. Any larvae that do form mature moths are unlikely to survive to lay more eggs because of the effects of the neem oil.