The leek moth, Acrolepiopsis assectella, is also sometimes referred to as the onion leaf miner. It is a pest found only in Europe, Asia, Africa, Siberia and parts of the United States. The leek moth is brown and attacks garlic, shallots, and chives in addition to leeks. Damage can be seen via brown and yellow patches on the leaves of the affected crops. Crop owners may even spot the silken cocoons on the leaves. Since second generations of leek moths do the most damage, they must be killed as soon as they are spotted.
Introduce natural predators to the affected crops. Frogs and beetles can be brought on to the property, while birds can be attracted to the area with birdfeeders. All three of these predators feast on moths and will kill the leek moths for you.
Set out pheromone traps to capture leek moths as soon as they emerge from their cocoons. This usually occurs in April and again in June. The traps will hold the moths until they die, and will prevent the moths from laying eggs that will produce another generation of leek moths.
Spray the leek moth infested crop with an insecticide that contains the active ingredient lambda-cyhalothrin. Follow the product label to accurately mix the insecticide with water and then apply it safely.
Kill the leek moths with Bacillus thuringiensis var. kurstaki (or Btk for short). Btk is a natural bacteria that grows on decaying matter. It is not harmful to humans or pets, but will kill any insects, including leek moths, that ingest it. Application must be made following packaging label instructions.
Dig the soil up during the winter months to disturb adults and pupae. Rotating crops will also help to keep leek moth populations down.
Severely infested crops may need to be destroyed.