Garden, How To, Vegetables

Leaf Miner – How to Identify & Manage this Garden Pest

Leaf miners are a super common pest found in the spring garden. They love the tender leafy greens and can cause a lot of damage if they are left unmanaged. But don’t worry, once you know more about them, they are a super easy garden pest to manage!

What are Leaf Miners?

Leaf miners are the larvae of different insects including flies, sawflies, moths or beetles. These insects lay eggs on their plant of choice, and once the eggs hatch the larvae burrow into the leaves and hollow out the inside of the leaves. This is why you see “squiggles” or lines in your leaves, as they move around eating.

How to Identify Leaf Miners & Their Damage

Young swiss chard leaves with leaf miner damage on them, seen as white trails through the leaves

Leaf miner damage appears as white/translucent spots or tunnels on leaves. Since the larvae is eating the centre of the leaf, the damage pattern is different on each leaf. Some will have large amounts of damage, while others may just have one small circle of damage. Others will be filled with squiggly lines as the larvae wanders around the leaf eating.

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Commonly Affected Plants

Swiss chard, spinach, beet greens, and cabbage are common plants that the leaf miner insects target.

Life Cycle of Leaf Miners

The parent insect of leaf miners will lay eggs (often on the underside of leaves), which will hatch into larvae that eat the inside tissue of leaves. Once they have finished this portion of their lives, they molt and mate, to lay more eggs and start the cycle again.

How to Control Leaf Miners

We never recommend using pesticides in a home garden. Leaf miner damage is never catastrophic, can always be managed and you won’t lose your crops to them. Therefore, pesticides are a total overkill solution to something that can be easily managed by yourself.

Option 1: Check for Eggs

A small, green swiss chard leaf has a cluster of 6 white eggs on the back of the leaf from the leaf miner

Now that you’re aware of the common plants affected by leaf miner, you can start watching for their eggs. Look on the underside of leaves for white eggs, laid in clusters. When you find these eggs, wipe them off. By doing this, you stop the larvae from hatching at all.

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Option 2: Remove Affected Leaves

A pile of swiss chard leaves on the ground with leaf miner damage in them

If you find affected leaves you can either remove the leaves, or, the best option is to harvest the leaves and cut the damaged parts out before you cook with them.

The photo above is the first year I ever learned about leaf miner. I panicked and pulled out ALL the leaves I found with damage. Some of the leaves were completely damaged (as seen on the far left of the photo), however other leaves barely had any damage. Yet I pulled them up to compost which is such a waste of good food. Learn from me, don’t be me, and just monitor your plants regularly.

Option 3: Remove the Insects

A napa cabbage leaf with leaf miner damage shown as a white patch on the leaf, and a small translucent worm shown

If you aren’t ready to harvest the leaves, and don’t want to remove them either, you can kill the larvae. You can either peel the damage open to find the larvae, or you can pinch the damaged areas and hope to get the larvae in that pinch, squishing it. In the photo above you can see a small, almost translucent insect on the inside of the folded over leaf. This is what you’re looking for.

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How to Prevent Leaf Miners

Preventing leaf miner is more difficult since they’re the larvae of a wide array of insects.

If you don’t want to do any of the control methods above, your next option would be to put insect netting over top of your plants. Since leaf miner mainly affects the leafy green plants, you don’t need to worry about pollinators accessing the plants. Therefore you can leave insect netting on from planting to harvest. Here are two recommendations for insect netting – West Coast Seeds and William Dam. If you choose to go the insect netting route, we recommend reading this article as it will help guide you through other common garden pests and how netting can benefit you against some of these pests as well.