If the leaves of your plants have what look like tiny, discolored, white trails popping up on them, then you have a leaf miner infestation. Unfortunately, there are different types of these pests, so they prey on various plants – not just one or two types, like other garden nuisances do.
What Exactly Are Leaf Miners?
Leaf miners are insect larvae that live on the leaves of plants. The trails, or tunnels, that they create on the leaves are caused when the larvae feed on the layers that have the least amount of cellulose. They leave droppings behind as well, which are sometimes seen on the leaves. Leaf miners damage the plants in more than cosmetic ways. The many layers that plant leaves consist of make them strong, and even those leaf miners don’t eat the cellulose-heavy sections, they are still weakening the entire structure. More obvious are the issues with vegetables that consist of edible leaves. Clearly, the ones that have been attacked by leaf miners are inedible and must be removed.
The larvae that act as leaf miners later become these types of insects: various beetles, sawflies (notably the Symphyta), flies (usually Diptera), and the Lepidoptera moth. Because the larvae are so small and live within the leaf’s structure, you won’t know that they are there until you see the telltale traces. The size, shape, and color of the tunnels will help you determine the types of larvae that are there. Simply removing the affected leaf doesn’t always work, because there might be leaf miners on the other ones that haven’t begun munching on the others yet.
How To Get Rid of These Pests
Thankfully, you can get rid of leaf miners using several different methods, none of which requires harsh chemical pesticides. In fact, leaf miners will not be effected by standard insecticides, because they live inside of the leaves, not on them. Therefore, the insecticide will not touch them. However, an organic insecticide, called Spinosad, will work. The leaf miners will ingest it, and then die. You may need to apply this compound at least three times per season to keep these pests at bay, and should be make sure to not spray it when bees are around, as it can harm them. Neem oil, which reduces the amount of larvae will work as well, but it is less effective, because it will not kill all of them.
If you don’t want to use any insecticides at all, there are some companion plants that will help with your leaf miner situation. They include a plant known as Pitseed Goosefoot, or lamb’s quarters; flowering columbines, and any of the four velvetleaf plants. Of them, two are native to North America, although they only grow in the more tropical regions of the country. All of these will attract the lead miners to them, thus keeping them away from your vegetable crop.
Although leaf miners can harm your plants, once you know how to manage them, your issues with them will be solved.
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Pic by Scott Nelson.