Leafminers are a common sight in plants of all types, but they are not usually a major threat to plants in themselves. However, they do leave unsightly tunnels that can drastically reduce the value of your crops if left untreated. The most common types of plants targeted are things like beans, lettuce, peppers, and anything that has susceptible leaves such as shade trees and flowers. Once you have identified a leafminer colony, there are a few methods to control and remove them from your home garden.
Method 1: Individual Crushing
Much like an actual mine shaft, leafminer tunnels are susceptible to collapse. Once you have spotted the patterns and discoloration of a tunnel, you can crush the larvae inside by applying pressure to the tunnel between two fingers. If caught early enough, this can solve an infestation before it ever spreads.
Method 2: Remove Unhealthy Plants
Leafminers are most attracted to plants that are already susceptible to pests or disease. By removing plants that are in less than optimal health, you can increase the likelihood that the leafminers will leave your healthier plants alone.
As you remove unhealthy plants, make sure to place them directly into trash bags and keep them stored far from your plants until they are picked up for removal. Never add them to your compost pile if they are infested with pests.
Method 3: Applying Floating Row Covers
Flies are the most common variety of leafminer encountered by home gardeners. These pests land on a suitable leaf and lay their eggs within the layers of the leaf tissue. A floating row cover will prevent flies from having access to the plants in the first place, which means eggs will not be present in the leaves.
Floating row covers can be found at your local home and garden stores at a relatively inexpensive price.
Method 4: Introducing Beneficial Insects
Because leafminers are actually the larvae of various insects, predators are more than happy to prey upon them whenever they are able. Predatory insects such as parasitic wasps are available for purchase that will prey upon leafminers and maintain pollination of your plants when applied to your garden areas, and are especially suited to indoor environments, where they don’t cause harm to people, pets, or plants.
Method 5: Setting Out Traps
Traps can be especially useful when attempting to contain flies and other mobile egg-laying insects. By laying down sticky traps lined with bait, you can prevent adults from getting to plants and laying eggs within them. This is surely a preventative measure; it will not solve the problem of any eggs already present within the leaves of a plant and will require further action to deal with larvae.
Method 6: Administering Neem Oil to Your Plants
Application of neem oil directly to the leaves of an infested plant will prevent larvae from reaching maturity, break their life cycle and repel the adult insects from landing on an affected leaf again. The oil must be applied as early as possible for best results — ideally just before or directly after eggs have been laid. This is a great solution to deal with both larvae and adult insects, but home gardeners must be precise in application to ensure effective control.
Method 7: Applying Pesticides
If you are left with no other options, pesticides can be used to deal with the adult insects laying eggs within each leaf. However, this is not generally the best course of action possible when dealing with leafminers; pesticide will only take care of the adults, not the larvae causing damage to your leaves. In addition, pesticides will also kill the natural predators of leafminers, so this should only be used as a last resort.
Leafminers may not be directly catastrophic to your plants, but they can cause the value of your plants to decrease and lead to other problems in plant health down the line. The best way to deal with a leafminer is to target the larvae within each leaf with direct crushing or neem oil, while dealing with the adults laying the eggs through covers, traps, or the introduction of beneficial predators. With vigilance and proper care, your plants can remain happy and healthy, free from damage caused by leafminers.