In the garden: Many flowers
On Crops: Leafy greens, peas, tomatoes
Worldwide, especially in mild winter climates
Meandering light trails in leaves are the eating paths left by leaf miners, which are the larvae of small black flies.
Leaf miner damage is usually cosmetic, though in severe case plants can be weakened.
Cover plants with garden fleece if you often see leaf miner damage in spinach or chard. Yellow sticky traps placed near plants can capture many adults before they lay eggs on plants but they should be used with caution in case they trap other beneficial bugs.
Pinch off, smash and compost badly damaged leaves. Spraying insecticides is of little use because the leaf miners are protected inside the leaves.
Many tiny wasps are leaf miner predators.