Aleaf miner is any one of numerous species ofinsects in which thelarval stage lives in, and eats, theleaftissue of plants. The vast majority of leaf-mining insects aremoths (Lepidoptera), sawflies (Symphyta, aparaphyletic group whichApocrita (wasps,bees andants) evolved from), and flies (Diptera). Somebeetles also exhibit this behavior.
Likewoodboring beetles, leaf miners are protected from manypredators and plant defenses by feeding within the tissues of the leaves, selectively eating only the layers that have the least amount ofcellulose. When consumingQuercus robur (English oak), they also selectively feed on tissues containing lower levels oftannin, a deterrent chemical produced in great abundance by the tree.[1]
The pattern of the feeding tunnel and the layer of the leaf being mined is often diagnostic of the insect responsible, sometimes even tospecies level. The mine often containsfrass, or droppings, and the pattern of frass deposition, mine shape, and host plant identity are useful to determine the species andinstar of the leaf miner. Some mining insects feed in other parts of a plant, such as the surface of afruit or the petal of a flower.
It has been suggested that some patterns of leaf variegation may be part of a defensive strategy employed by plants to deceive adult leaf miners into thinking that a leaf has already been preyed upon.[2][3]
Leaf miners are regarded aspests by many farmers and gardeners as they can cause damage toagricultural crops andgarden plants, and can be difficult to control withinsecticide sprays as they are protected inside the plant's leaves. Spraying the infected plants withspinosad, an organic insecticide, can control some leaf miners. Spinosad does not kill on contact and must be ingested by the leaf miner. Two or three applications may be required in a season. However, this will have harmful ecological effects, especially if sprayed when bees or other beneficial arthropods are present.[4][5]
Leaf miner infection of crops can be reduced or prevented by plantingtrap crops near the plants to be protected. For example,lambsquarter andcolumbine will distract leaf miners, drawing them to those plants and therefore reducing the incidence of attack on nearby crops. This is a method ofcompanion planting.[6]
