Leaf miners are the larvae of small flies that lay eggs in the leaves of tomato plants. When the eggs hatch, the larvae eat the interior layer of the leaves, leaving trails called mines. Leaf miners can cause leaves to die and drop off. Though the larvae only feed on the tomato leaves for two weeks, seven or eight generations of leaf miners can feed each summer. Heavy infestations can kill tomato plants.
Monitor plants for damage. If only a few leaves are damaged, pick off these leaves and destroy them. If one or two plants are affected, the best control is to uproot and destroy these plants, which will destroy any leaf miner larvae and eggs on the plants.
Spray the leaves of affected tomato plants with an organic insecticide containing spinosad. This insecticide is approved for use on organic crops, and it won't harm beneficial insects.
Hang flypaper in greenhouses to capture leaf miner flies before they have a chance to lay their eggs.
Purchase parasitic wasps Diglyphus begini or Chrysocharis parksi and release them into the garden. The University of California Agricultural and Natural Resources department recommends these wasps as effective biological controls against leaf miners.