It’s always such a headache when pests come to visit your garden. Allium leaf miners are relatively new to the United States but can cause a lot of damage in a short time. Read on to find out how to prevent them and how to control them.
How to control allium leaf miners: Allium leaf miners are insects that are hazardous to plants such as garlic, leeks, and onions. During the larvae stage, they burrow through the leaves and stems. To prevent the flies from laying eggs, add a mesh row cover. Black or silver plastic mulch is also effective at prevention. If you notice damage from allium leaf miners, use an organic pesticide.
What is an allium leaf miner?
This pest is considered invasive and is not so slowly making its way around the United States, causing terrible destruction. Allium leaf miner is named because it attacks plants in the allium family, including onions, garlic, shallots, leeks, and chives.
The larvae of allium leaf miners burrow into plants of the allium family, eventually getting to the heart of the plant in the bulb. Then, they pupate.
The burrowing severely weakens the structure of the allium plants which then makes them susceptible to bacterial and fungal infections.
While allium leaf miner was first discovered in Europe in the 1850s, it is now in the United States. The pests were first seen in the eastern United States in 2015 and 2016 and they are now making their way across the country.
How do you identify allium leaf miners from other pests?
Allium leaf miner larvae are quite tiny, measuring just 8mm in length. They are legless and look more like tiny seeds than bugs. They are a light yellow or cream color, which can stand out against a darker green or bright white plant.
There are many other pests that are this size so if you want to distinguish what you are dealing with, another prevalent pest is the leek moth larvae which have legs and a defined head.
Once allium leaf miners become adults, they will be even smaller as they are just 3 mm long. They look like tiny flies with black or grey bodies and yellow heads.
Again, for comparison, onion maggots, which are quite common, will have longer bodies.
Instead of trying to see if you have allium leaf miners, the more common way of identifying them is by the damage on the leaves. You will see tiny oval markings all along the stem of an onion or garlic plant, which indicates their presence.
You may also see tunnel-like strips on your plants which are created as the miners borrow their way through the plant.
Other signs that you have an allium leaf miner infestation include distorted plants and stunted growth.
The time when allium leaf miners are the most destructive is when they are in the larvae stage. This is the time when they burrow through the plant leaves and stems, leaving them in a weakened state.
Placing sticky traps around your garden can help determine what pests are currently in your garden. You can then look at the traps and identify if there are good or bad insects.
If you aren’t sure what you are looking at, you can head to a gardening center or look for images online. Alternatively, you can download apps that will help you learn more about certain insects.
Place the sticky traps in your garden during late winter or early spring and then inspect them every week to see if any new pests have come along.
During late summer, allium leaf miners will reproduce so you can set the traps again during this time to monitor for their presence.
The first indication that you have allium leaf miners is often the destruction that they cause. However, if you see these patterns early, you may still have time to stop them from taking over.
Look for leaves that are curly or wavy as this can be a sign that your plants are weakened.
The biggest sign of damage is if there is a trail or tunnel through your plant. Allium leaf miners will start on the outer edges and then tunnel toward the bulb, so you may see a lighter-colored line that indicates movement.
How to deal with allium leaf miners?
Unfortunately, once you have an infestation of allium leaf miners, there aren’t many options. Unlike other bugs, such as aphids which stay on the outside of plants, miners burrow into the plants or lodge themselves deep in the layers of allium bulbs.
An insecticide, preferably an organic one, is the best option.
Spinosad is a good insecticide. It is organic and made from the fermentation of bacteria. Apply it to the roots of your allium plants to both prevent and kill allium leaf miners.
How to prevent allium leaf miners?
One of the easiest ways to prevent allium leaf miners is by using floating row covers. These act like netting and the holes in the mesh are too small to allow the insects through. However, light and water can get through.
In order for the row covers to be effective, you need to place them over your crops in spring, or you can be even more proactive and do so in early fall.
Adult flies will lay their eggs in your allium plants, so the row covers act to prevent this from happening. If you add the nets too late, the flies will already have done their damage.
Interestingly, if you place a layer of plastic mulch over the ground you are growing your garlic or onions, allium leaf miners will be less interested in infecting your plants. The plastic needs to be black or a reflective silver color.
This is not a foolproof plan, as the pests aren’t prevented from eating the plants but rather are deterred from the reflective material.
Allium leaf miners attack plants in the allium family, such as garlic and onions. Use plastic mulch and row covers to prevent them from eating your plants. If you do have an infestation, use an organic pesticide to tackle them.