When you noticed that the leaves of your vegetable has serpentine mines that wind snake-like across the leaves, that is a problem similar to all other farmers and gardeners. It is called leafminer.
Leafminers are larvae of various insects including beetles, flies and moths. These larvae are very small with a size of 1/5 of an inch or 1/8 of an inch in length. They live inside the leaves of plants and trees, feeding on the soft inner plant tissue between the upper and lower sides of the leaf. Adults lay their eggs in clusters just under the surface of the leaf epidermis. The larvae mine leaves for 1 to 3 weeks till mature, then drops down to the soil and pupates for 2 to 4 weeks.
Although the larvae damage has little or no effect on plant growth and is not fatal to larger plant, but the case is different with regard to plants in the seedling stage of growth. If you will not prevent them early, the extreme population of leafminers may slow your plant growth. If they infested your edible plants, this will result in financial loss because the plant is no longer marketable.
Preventing leafminers requires a lot of observation because even if you spray them with insecticide they will not be killed because they are inside the leaves. You have to time this perfectly so that the pesticide kills the larva and adult flies. If you spray too early, the insecticide will not injure the eggs or the adult flies.
How to Prevent Leafminer?
There are several ways to prevent leafminers but it requires patience and keen observation. Here are some of the solutions in preventing leafminers.
- Check your seedlings for leafminers’ damage before transplanting them in your vegetable garden.
- Cover Plants. Use fine smooth white cloth to keep adults from laying eggs on leaves especially small seedlings.
- Immediately pick infested leaves and destroy it, do not leave it near the plants. Once you have spotted the patterns of a tunnel, you can crush the larvae inside by applying pressure to the tunnel between two fingers. If caught early,this can solve an infestation before it even spreads.
- Plant trap crops. Their population can be prevented by planting plant trap crops near the plants most targeted by leafminer.
- Use Neem oil. Spray with neem oil to disrupt the life cycle of the insects to the point they do not feed, fly or mate. Spray daily for a week.
- Encourage parasitic wasps in your plant. The wasps lay their eggs inside the leafminers. When the eggs hatch, the hatchlings will feed on them, thereby killing them. These wasps also feed on leafminer larvae and can significantly reduce leafminer population. In some countries, parasitic wasps is produced and sold to farmers to kill these leafminers.
- Till your soil after harvesting your vegetable especially if there has been leafminer infestation. This will reduce leafminers infestation.
- Look for egg clusters on plants regularly and destroy them as soon as they are visible.
- Plant vegetable varieties that are susceptible to leafminer infestation.
- Use sticky traps to catch egg laying adults.
- Keep your plants healthy. Remove unhealthy plants. Leafminers are most attracted to plants that are already susceptible to pests and diseases. By removing plants that are less than optimal health, you can increase the likelihood that the leafminers will leave your healthier plants alone.
- Keep plants well-watered to help keep them healthy and vigorous.
- As mentioned earlier, you need to time this if you will use insecticide, organic or non-organic. To do this, you’ll need to do a little testing. Locate some leaves in your garden that are infested with leaf miners. Place these into a sealed plastic bag and check the bag everyday. When you see that the leaf miner larva have become adults, you’ll know that it is time to start spraying your plants. Begin immediately, and spray your plants everyday for 7 days. This is the most effective use of insecticide for leafminer.