Leaf miner

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Leaf miner damage to a horse chestnut tree

Leaf miners are insect larvae that live within leaf tissue. Many cause damage to garden plants and crops.

Like wood borers, leaf miners are difficult to control as they are protected from insecticide sprays and plant defenses by feeding within the tissues of the leaves themselves, selectively eating only the layers that have the least amount of cellulose. The precise pattern formed by the feeding tunnel is very often diagnostic for which kind of insect is responsible, sometimes even to genus level. The mine often contains frass, or droppings, and the pattern of frass deposition, mine shape and host plant identity are useful to determine the species of leaf miner. The vast majority of leaf-mining insects are moths (Lepidoptera) and flies (Diptera), though some beetles and wasps also exhibit this behavior. A few mining insects utilise other parts of a plant, such as the surface of a fruit.