Leafminer Control: How to Identify, Prevent and Get Rid of Leafminers

Leafminers are some of the most common concerns amongst gardeners because they cause unattractive leaves. While they do not cause any direct injury to the host plant, they will give it an unsightly appearance. For this reason, it is important to be aware of how to get rid of leafminers.

It is important to note that leafminer does not refer to a specific type of pest. Rather, it is a collective term for a number of insects that are in their larval stage. They mine on the leaves of the plant, which is exactly where their name is from. Some of the insects that fall into this category include beetles, wasps, moths, and flies. With this, there are variations in their appearance. Since they are larvae, they appear like maggots. They are usually yellow and has a length of 1/8 inch.

Leafminer

Leafminers on a Green Leaf

Leafminer’s Habitat

From their name, it is pretty much obvious that they live on the leaves of their host. They can appear in different areas, depending on the specific type of the insect. Like other insects, they undergo a complete transformation in different stages – egg, larva, pupa, and adult. It is during their larval stage when they feed on the leaves. When they are eggs, meanwhile, they overwinter in the soil. Once they enter the pupal and adult stage, on the other hand, the physical appearance will vary. Some of them are also not as destructive as they are when they mature as against to being a larva.

Identifying Leafminer’s Damage

Plants Affected

Because of the diversity of leafminers, they feed on a wide array of plants. In broadleaf trees, they are common in poplar, aspen, hawthorn, and elm. Meanwhile, in vegetables, they feed on lettuce, peas, tomatoes, beans, and cabbages. Lastly, for flowering plants, some of the most popular targets are marigold, impatiens, petunia, dahlia, and begonia.

Symptoms

The following are some of the most common symptoms that will be indicative of the presence of leafminers:

  • Among others, the presence of holes in plants is indicative that leafminers are infesting your garden. Like most insects in their larval stage, they feed on the underside or above the leaf, which is why this is where the damage can be seen.
  • Aside from the holes, they can also cause discoloration in the leaf. It may turn yellow. This is because once there are holes, they are unable to absorb the nutrients that they need, and hence, causing the leaf to die.
  • The leaves will also appear curvy or curly. A zig-zag line can appear on the surface, which is a trace of where the larvae were feeding.

Results of Infestation

In most instances, the leaf miners do not cause severe damages to their host plant. Unlike other pests, there is a small likelihood that they will result in death. This is especially true in the case of larger hosts. When they attack plants at a young age, however, they are more susceptible and destructive. They can damage the tissue even before they grow, causing negative impacts on the plant. Most of the damages are purely aesthetics. In the case of crops, this might render the produce unmarketable, and hence, will result in economic loss.

Leafminer Damages

Most of the Leafminer’s Damages are Purely Aesthetics

How to Get Rid of Leafminers

Natural and Organic Solutions

Here is a quick list of some of the most effective natural and safe control measures for the elimination of leafminers:

  • Protection is one of the first things to do. This does not only prevent future infestation, but also helps to keep the population in check. This makes sure that they will not grow large in numbers. With this, consider the installation of row covers, especially for plants that do not need pollination to survive. A cold cap will also be effective for protection.
  • The use of natural pesticides is also a good idea. Most people instantly cringe when they hear the word pesticides, thinking that they have toxic chemicals. There are biological and natural insecticides that are free from synthetic ingredients. One of the perfect examples of this is neem oil, which does not cause any harm to the environment.
  • Handpicking the larvae may seem like an exhausting task, but this is an effective solution as well. This works best if the population and the garden are just small. Spot larvae feeding on the leaves, take them out, and place in a bucket of soapy water. This will kill them. Avoid throwing the larvae just anywhere in the garden as they will just find their way back to the host plant.
  • There are also natural predators that will be helpful. One of the perfect examples of the latter is Diglyphus isaea or a parasitic wasp. With a size of just 2mm, it stings the leafminer and kills it. Chrysocharis parksi will also help. Both of these wasps are commercially-available.
  • Aside from wasps, other effective natural predators that you can have in the garden are spiders and green lacewings. They will feed on the larvae to prevent damages on the host plant. These insects are also available for commercial sale. Do not use any chemical sprays as they can also kill the natural predators.

Chemical Solutions

For a long time now, chemical control is one of the most common solutions for the elimination of leafminers. Because they are in their larval stage, it is easier to kill them as against when they fully mature. One of the most common is oxamyl, which works by blocking the nervous system of the pest and will lead to its death. Other active components that work in the same way include dimethoate, esfenvalerate, and diazinon. The use of chemicals, however, is the last thing you have to consider as it can kill even the beneficial insects in the garden.

How to Prevent Leafminers

One of the best ways to prevent their presence is to keep the environment clean. Whether it is in the garden or commercial plantations, it is important to get rid of decaying vegetation and other forms of trash. They will encourage the presence of pests, which will lay eggs and turn into damaging larvae.

Another preventive measure that will work is planting varieties that will resist the growth of leafminers. By doing this, you will never have to think about the pest and the damages they bring.

Lastly, the best thing that you can do is to improve the health of the plant. Frequent monitoring is a must to deal with the problem early on before they can wreak havoc. Provide the plants with the nutrients that it needs, which will make it more resistant to infestations.

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