Leaf miners
Larvae of small flies and moths that tunnel inside leaves, leaving pale, winding trails.
Also known as: Citrus leaf miner, Serpentine leaf miner
Symptoms and identification
Silvery, white or pale winding lines or blotches inside the leaf, often with a dark line of droppings. On citrus, new leaves curl and twist with shiny trails. Heavily mined leaves turn yellow and drop.
Causes
Adult flies or moths lay eggs in young leaves; the larvae feed between the leaf surfaces, protected from contact sprays. Flushes of soft new growth attract them.
Organic treatment
Pick off affected leaves or squash the larva inside the mine. Spray neem oil on new growth every 7 days during flushes; it deters egg-laying and affects young larvae.
Prevention
Remove and destroy mined leaves early. Avoid heavy nitrogen feeding that produces repeated soft flushes, and use yellow sticky traps to catch adult flies.
Chemical treatment (use with care)
Systemic insecticides labelled for leaf miners can be used on ornamentals following the label. On fruit and vegetables, use only products approved for the crop.