On a bright and sunny morning, you go to check on your plants in the garden or greenhouse. Instead of healthy growth, you find they are looking wilted or marked by slimy white wavy lines.
These are the signs that the eggs of leaf miners that have been nestling snugly inside your plant’s leaves have developed into larvae.
The maggots are now busy feeding on the sap, forming tunnels along the leaves of the plants. The critters may be wasps or moths but often are very unwanted tiny black flies.
Time for action, but you don’t want to use synthetic chemicals, so what eco-friendly treatments are there? Fortunately, there are plenty.
Here are some tips on how to get rid of leaf miners naturally.
1. Beneficial Insects
There are many helpful bugs and insects in the garden that enjoy having a feast out of destructive insects.
Lady beetles (ladybirds), lacewings, praying mantises, ground beetles, and soldier bugs help in the biological control of harmful insects.
Parasitic wasps are the main predators of leaf miners. Find more details below.
2. Hot Pepper Spray
This organic method can be bought ready-made but is also easily prepared at home. Various recipes for this are found on the internet but here’s an easy one.
Combine cayenne pepper, onion or garlic, organic liquid soap, and water in a blender. Blend them up and then strain.
Spray frequently, especially on the undersides of leaves.
3. Neem Oil
Widely used in organic farming today, this vegetable oil, derived from the neem tree is effective against attacks by many pests including leafminers.
It can also be utilized for keeping the garden clear of mildew and fungus.
Keeping a ‘clean’ garden will naturally deter infestations from destructive insects.
4. Row Covers
A cover, usually made from a synthetic material like polyethylene, is placed over rows of developing plants or crops.
The cover is supported by a framework of wire hoops or wooden cages to protect the young growth from harmful insects. This also gives protection from birds, domestic pets, night frosts, or daytime sun damage.
Variations can be bought or constructed homemade from fine mesh or other suitable lightweight fabrics.
WeedGuard is also used by growers to cover the soil. This helps to prevent any larvae from dropping down and burrowing for later development.
The covers can be removed once the growing season is over.
5. Till the Soil
One of three simple measures to protect your plants from an infestation.
Tilling the soil after harvest can destroy any pupae in the earth and prevent adult flies from emerging in the spring.
6. Sticky Traps
An old way of dealing effectively with pesky insects. These colored strips of sticky material attract pests who become stuck, unable to mate, lay eggs, or survive.
Sticky traps are particularly useful, hung in greenhouses, or for indoor plants. It is known that different colors attract different pests, with yellow or bright blue both being high attractants to leaf miners.
7. Remove the Eggs
Removing the eggs by hand at the outset of any sign of the pests may be tedious but also effective.
A naturally occurring insecticide found in the soil; sold as a liquid soap spray and as a fermented product allowed and used in organic farming.
You may wish to try spraying Spinosad on the leaves for direct contact with the miners.
The effect of the insecticidal soap paralyzes the critters and kills them in a day or two. More than one application may be needed in a growing season.
If you have concerns about the toxicity of Spinosad, manufacturers state that it rates as low toxicity for mammals. However, it has high toxicity for bees, the essential pollinators of plants, and crops in the ecosystem.
Therefore, evening spraying, or zero sprayings in the flowering period of plants, may make this treatment more useful for severe or persistent infestations.
9. Beneficial Nematodes
This is an increasingly popular form of pest control. Beneficial nematodes are tiny organisms occurring naturally in the soil.
These microscopic roundworms are capable of destroying many garden pests at the developmental stage in the earth. They will also attack and kill adult leafminers overwintering comfortably in the garden soil before they can mate and lay eggs in your plants.
Nematodes act by entering the gut of the insect and releasing bacteria that cause blood poisoning and death. They then feed off the dead matter until no further food is available, obliging them to seek new hosts to kill.
The constant food source causes the nematodes to grow and multiply, naturally breaking the cycle of infestation.
10. Parasitic Wasps
There are two types of parasitic wasps, namely Diglyphus begini and Chrysocharis parksi that kill leaf miners.
After laying eggs, the pupae of the wasps feed on the dead pest and clear the plant of the problem.
Using insecticides could prevent this natural solution by killing off the predators as well as their prey and tainting future growth.
Where leafminers can affect edible plants like tomatoes, spinach, other greens, and salad vegetables, this is an important consideration. Plant dill, yarrow, cosmos, fennel, etc., to attract them.
11. Diatomaceous Earth
Also known as fossil shell flour, this product has been used for many years as an anti-caking agent in animal feed.
It is sand composed of the fossilized crushed and powdered shells of minute aquatic creatures.
In pest control, diatomaceous earth is processed in a way that causes dehydration in some insects and is effective in controlling leaf miner infestation.
It can be made into a spray or used in raw powder form. One down point to consider is that, used as a powder sprinkled directly onto plants, a shower of rain will mean re-application.
12. Trap Crops
These are plants that have attractant properties and are grown in large stands to lure various pests away from the main plants/crops.
They are sometimes called ‘sacrificial’ plants and therefore this method is generally more suited to commercial enterprises.
Trap crops that leaf miners will attack include radish, chickweed, pigweed, velvetleaf, and plantain.
This will greatly assist in keeping the plants healthy and enable early viewing of any possible infestation. Infected leaves can be removed, crushed, and disposed of.
It is so disheartening to spend time and effort in producing fine plants only to see them destroyed by pests like leaf miners.
Commercial pesticides are available, but fortunately, there are also many natural solutions to treat the problem.