Larva of an insect that lives in and eats the leaf tissue of plants
Leaf miner damage to ahorse chestnut treeLeaf with minor miner damageTomato with leaf miner damageLeaf mines by the mothPhyllocnistis hyperpersea on aPersea borbonia leaf. The red arrow indicates the pupal crypt.Leaf miner trail on a fallen leaf in aGondwana cool temperate rainforest. Note the initial thin width of the insect trail, becoming wider as the insect grows while it navigates around the leaf.Cryptocarya foveolata from Cobark Park,Barrington Tops,Australia
Aleaf miner is alarval stage of various insect species that live and feed within the tissues of a plants leaves. The term does not describe a single taxonomic group, but rather a feeding behavior known as "leaf mining" that has evolved independently across several insect orders. Leaf miners are considered both ecologically significant and economically important because of their role in ecosystems and their impact on agriculture and horticulture. Leaf miners consume the inner tissues of leaves while leaving the outer epidermal layers largely intact. This results in distinctive patterns or "mines" on the leaves, which can appear as winding trails, blotches, or tunnels. Leaf mining is an ancient ecological strategy that has been employed by insect larvae since at least the beginning of thePermian period, around 295 million years ago.[1]
Adult leaf mining insects typically lay eggs on or within the surface of a host plants leaf. When the larvae hatch, they burrow into the leaf and begin feeding between the epidermal layers. Much likewoodboring beetles, leaf miners are protected from manypredators while feeding within the tissues of the leaves,[3] selectively eating only the layers that have the least amount ofcellulose. After completing larval development, the insect pupates either inside the mine, on the leaf surface of the leaf or within the soil below the host plant depending on the species. Emerging adult insects can then continue their cycle.
Plants have developed a variety of defense strategies to reduce damage from leaf miners. These defenses can be structural, chemical, or physiological and may act either directly against the larvae or indirectly by attracting natural enemies.
Leaf toughness and thickness: Some species of leaf mining insect will only lay eggs on the younger leaves of its specific host plant.[4] The older and larger leaves oforange trees such asCitrus × sinensis can resist infestation from the citrus leaf miner (Phyllocnistis citrella), however the younger thinner leaves are highly susceptible.[5]
Trichomes (leaf hairs): Plants that possess trichomes on their leaves have been found to deter leaf miners.[6] The plant speciesSolanum pennellii possesses leaves covered in tiny hairs, which make it resistant to the leaf mining flyLiriomyza trifollii. The cultivated tomato (Solanum lycopersicum) however doesn't possess as much trichomes therefore is much more suscpectible to the leaf miner.[6]
Leaf variegation: Plants can sometimes evolve to use leafvariegation in order to mimic leaf miner damage, this then makes the plant less appealing to leaf mining insects that seek a healthy host plant to desposit their eggs. It is believed that some patterns of leaf variegation are adaptations used by plants to deceive adult leaf miners into mistaking the variegated leaf as one that is already hosting a larval leaf miner.[7] The plant speciesCaladium steudnerifolium can possess individuals with leaves that exhibit variegation that strongly resembles the leaf damage caused by the larvae of leaf miners. Infestations of leaf miner were found to be signficantly higher inC. steudnerifolium leaves that lacked variegatation.[8]
Tannins: Plants will utalize a variety of organicpolyphenolic compounds such astannins to poison and deter insect herbivores.[9] Leaves containing high tannin levels have been found to cause leaf miningCameraria to become more susceptible toparasitism from parasitic species ofHymenoptera. High tannin levels within consumed leaves were also found to affected the development of larva by causing a decrease in weight in the developing pupa.[10]
Saponins: Tree species such as the Red buckeye (Aesculuspavia) producessaponins within its leaves to aid leaf resistance against the larvae of the Horse Chestnut Leafminer (Cameraria ohridella).[11]
Leaf abscission: Some plants can shed their leaves when affected by leaf miners in a process known asabscission. The arroyo willow (Salix lasiolepis) will often release leaves that contain the larva of leaf miningPhyllonorycter species. This process has been found to greatly reduce the survival rates ofPhyllonorycter larva within the abscised leaves.[12]
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.
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.[13][14]
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.[15]
^Nawaz R, Abbasi NA, Hafiz IA, Khan MF, Khalid A. Environmental variables influence the developmental stages of the citrus leafminer, infestation level and mined leaves physiological response of Kinnow mandarin.Sci Rep. 2021;11(1):7720. Published 2021 Apr 8. doi:10.1038/s41598-021-87160-8
^abHawthorne, D. J., J. A. Shapiro, W. M. Tingey, and M. A. Mutschler. 1992. "Trichome-Borne and Artificially Applied Acylsugars of Wild Tomato Deter Feeding and Oviposition of the LeafminerLiriomyza trifolii."Entomologia Experimentalis et Applicata 65 (1): 65–73. https://doi.org/10.1111/j.1570-7458.1992.tb01628.x.
^Materska, M., Pabich, M., Sachadyn-Król, M., Konarska, A., Weryszko-Chmielewska, E., Chilczuk, B., Staszowska-Karkut, M., Jackowska, I., & Dmitruk, M. (2022). The Secondary Metabolites Profile in Horse Chestnut Leaves Infested with Horse-Chestnut Leaf Miner.Molecules (Basel, Switzerland),27(17), 5471. https://doi.org/10.3390/molecules27175471
^Faeth, Stanley H., and Thomas L. Bultman. 1986. "Interacting Effects of Increased Tannin Levels on Leaf-Mining Insects."Entomologia Experimentalis et Applicata 40 (3): 297–301. https://doi.org/10.1111/j.1570-7458.1986.tb00515.x
^Ferracini, Chiara, Paolo Curir, Marcello Dolci, Virginia Lanzotti, and Alberto Alma. 2010. "Aesculus pavia Foliar Saponins: Defensive Role against the LeafminerCameraria ohridella."Pest Management Science 66 (4): 399–405. https://doi.org/10.1002/ps.1940
^Preszler, Ralph W., and Peter W. Price. 1993. "The Influence ofSalix Leaf Abscission on Leaf-Miner Survival and Life History."Ecological Entomology 18 (2): 150–154. https://doi.org/10.1111/j.1365-2311.1993.tb01196.x
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The leaf and stem mines of British flies and other insects. Includes illustrated keys for identification of mines by host-plant genus and detailed descriptions of over 900 species along with their distribution in Great Britain and Northern Ireland and elsewhere.
