Dryocosmus kuriphilus | |
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Species: | D. kuriphilus |
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Dryocosmus kuriphilus Yasumatsu, 1951 | |
Dryocosmus kuriphilus is a species of gall wasp known by the common names chestnut gall wasp, Oriental chestnut gall wasp, and Asian chestnut gall wasp. It is native to China and it is known in many other parts of the world, particularly the Northern Hemisphere, as an introduced species and an invasive horticultural pest. It attacks many species of chestnut (genus Castanea), including most cultivated varieties. It is considered the world's worst pest of chestnuts. [1]
When it was first discovered, the wasp was considered to be a species of Biorhiza . It was given its current name in 1951, when it was formally described. [2] By this time it had invaded Japan and was attacking chestnuts there. [3] It is now in Korea, Nepal, [4] Italy, Slovenia, [5] France, [6] Switzerland [7] and other parts of Europe, and the southeastern United States. [2]
The adult female wasp is 2.5 to 3 millimeters long and shiny black in color with brown legs. It produces stalked white eggs, each about 0.2 millimeters long, and the larva is white and about 2.5 millimeters long. The adult male of the species has never been observed. [2]
The female lays eggs in the buds of chestnut trees, sometimes producing over 100 eggs. [2] The wasp is thelytokous, producing fertile eggs by parthenogenesis, without fertilization by a male. Oviposition occurs in the summer. Larvae hatch from the eggs but do not begin growing immediately. Their growth begins the following spring, when the tree buds begin to develop. At this time, the larvae induce the formation of galls on the tree. [8] The galls are green or pinkish and up to 2 centimeters wide. [2] The larvae develop inside the protective gall structures and emerge from them as adults. The galls dry out and become woody. The galls can be very damaging to the tree. [8] They occur on the new growth of the tree, disrupting the fruiting process, and can reduce a tree's yield up to 70%. They are even known to kill trees. [1] The wasp can fly, but it is distributed to new territory more often by human activity, [9] such as the planting of new trees and the transport of infested wood. [5]
The presence of galls can also increase the likelihood of the tree's becoming infected with chestnut blight, a condition caused by the fungus Cryphonectria parasitica. The opened gall left by the wasp after it matures and departs may be an entrance through which the fungus can infest the tree's tissues. [7] The galls can also become infected by the sweet chestnut pathogen Gnomoniopsis smithogilvyi . [10]
Chestnut species affected by the gall wasp include Japanese chestnut (Castanea crenata), American chestnut (C. dentata), Chinese chestnut (C. mollissima), European chestnut (C. sativa), Seguin chestnut (C. seguinii), Henry's chinquapin (C. henryi), [9] and hybrids. So far it has not been observed on the Allegheny chinquapin (C. pumila). [2]
Control measures include pruning infested buds off of trees and protecting buds with netting. These methods are not practical for large numbers of trees, such as commercial orchards. In China, with lower labor costs, Chinese chinquapin ( Castanea seguinii ) is used as a trap crop. By planting a hedge of C. seguinii around C. mollissima (Chinese chestnut) orchards, the wasps will first encounter and attack the buds of the less valuable C. seguinii, allowing the galled twigs to be cut off and destroyed. [11] Pesticides are generally not effective because the insects take cover inside the galls. [9] One gall wasp control method which has been successful is the introduction of the torymid wasp Torymus sinensis . This parasitoid is used as an agent of biological pest control against the gall wasp in Japan. Research is underway to determine where else it might be appropriate to release the parasitoid. [12] [13] A number of other parasitoids have been noted with the gall wasp, including the torymids Torymus beneficus , T. geranii , and Megastigmus nipponicus , the ormyrid wasps Ormyris punctiger and O. flavitibialis , and the eurytomid wasps Eurytoma brunniventris and E. setigera . These species do not make effective control agents, as their rates of parasitism are not high. [14]
The American chestnut is a large, fast-growing deciduous tree of the beech family native to eastern North America. As is true of all species in the genus Castanea, the American chestnut produces burred fruit with edible nuts. The American chestnut was one of the most important forest trees throughout its range.
The pathogenic fungus Cryphonectria parasitica is a member of the Ascomycota. This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America in the early 1900s. The fungus spread rapidly and caused significant tree loss in both regions.
Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.
Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" (petiole) formed between the first two segments of the actual abdomen; the first abdominal segment is fused to the thorax, and is called the propodeum. Therefore, it is general practice, when discussing the body of an apocritan in a technical sense, to refer to the mesosoma and metasoma rather than the "thorax" and "abdomen", respectively. The evolution of a constricted waist was an important adaption for the parasitoid lifestyle of the ancestral apocritan, allowing more maneuverability of the female's ovipositor. The ovipositor either extends freely or is retracted, and may be developed into a stinger for both defense and paralyzing prey. Larvae are legless and blind, and either feed inside a host or in a nest cell provisioned by their mothers.
The emerald ash borer, also known by the acronym EAB, is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash species. Females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years. In its native range, it is typically found at low densities and does not cause significant damage to trees native to the area. Outside its native range, it is an invasive species and is highly destructive to ash trees native to Europe and North America. Before it was found in North America, very little was known about emerald ash borer in its native range; this has resulted in much of the research on its biology being focused in North America. Local governments in North America are attempting to control it by monitoring its spread, diversifying tree species, and through the use of insecticides and biological control.
A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two other insect orders, the Diptera and Coleoptera (beetles). Seventeen families in Hymenoptera and a few species of Diptera and Coleoptera are hyperparasitic. Hyperparasitism developed from primary parasitism, which evolved in the Jurassic period in the Hymenoptera. Hyperparasitism intrigues entomologists because of its multidisciplinary relationship to evolution, ecology, behavior, biological control, taxonomy, and mathematical models.
The winter moth is a moth of the family Geometridae. It is an abundant species in Europe and the Near East and a famous study organism for evaluating insect population dynamics. It is one of very few lepidopterans of temperate regions in which adults are active in late autumn and early winter. The adults use endothermy for movement in these cold temperatures. The females of this species are virtually wingless and cannot fly, but the males are fully winged and fly strongly. After the initial frosts of late fall, the females emerge from their pupae, walk to and up trees and emit pheromones in the evening to attract males. After fertilization, they ascend to lay, on average, around 100 eggs each. Typically, the larger the female moth is, the more eggs she lays.
Cryphonectria is a fungal genus in the order Diaporthales. The most well-known and well-studied species in the genus is Cryphonectria parasitica, the species which causes chestnut blight. The genus was, for a time, considered synonymous with Endothia, but the two are now recognised as distinct. Taxonomic studies in 2006 limited the genus to four species, but a fifth, Cryphonectria naterciae, was described in 2011 from Portugal.
Castanea mollissima, also known as the Chinese chestnut, is a member of the family Fagaceae, and a species of chestnut native to China, Taiwan, and Korea.
Andricus kollari, also known as the marble gall wasp, is a parthenogenetic species of wasp which causes the formation of marble galls on oak trees. Synonyms for the species include Cynips kollari, Andricus quercusgemmae, A. minor, A. indigenus and A. circulans.
Peridroma saucia, the pearly underwing or variegated cutworm, is a moth of the family Noctuidae. The species was first described by Jacob Hübner in 1808. It is found in North and South America, Europe, Asia and Africa. The variegated cutworm feeds on many plants, especially common fruits and vegetables. The moth undergoes two to four generations per year. The development of the moth slows in colder temperatures, indicative of its migratory nature. All stages of the life cycle have a developmental threshold for temperature. The moth is known to migrate to the northern regions during warmer months, returning to the southern regions when the climate becomes colder.
Hypovirus is a genus of viruses, in the family Hypoviridae. Fungi serve as natural hosts. There are four species in this genus. Infection reduces the virulence of its parasitic host, making it a hyperparasite useful for blight control.
Leptocybe invasa, the blue gum chalcid wasp or eucalyptus gall wasp, is a chalcid wasp which is the only species in the monotypic genus Leptocybe in the subfamily Tetrastichinae, of the family Eulophidae. It is a gall wasp which causes the formation of galls on a number of species of Eucalyptus, it was described in 2004 after galls were found in river red gums in the Mediterranean and Middle East and has since been found to be a widespread species where its host trees are planted. It is indigenous to Australia.
Tetrastichus planipennisi is a parasitic non-stinging wasp of the family Eulophidae which is native to North Asia. It is a parasitoid of the emerald ash borer, an invasive species which has destroyed tens of millions of ash trees in its introduced range in North America. As part of the campaign against the emerald ash borer (EAB), American scientists in conjunction with the Chinese Academy of Forestry searched since 2003 for its natural enemies in the wild leading to the discovery of several parasitoid wasps, including Tetrastichus planipennisi which is a gregarious endoparasitoid of EAB larvae on Manchurian Ash and has been recorded to attack and kill up to 50 percent of EAB larvae.
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Marsol is a natural chestnut hybrid, a cross between a European chestnut and Japanese.
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Gnomoniopsis castaneae is a fungus of the order Diaporthales that is the most important cause of brown chestnut rot, an emerging disease that damages the fruit of chestnuts. It also causes cankers and necrosis on leaves and on chestnut galls caused by the gall wasp, Dryocosmus kuriphilus. Additionally, it can cause cankers on hazelnut trees, less severe damage to some nut trees, and lives as an endophyte on other nut trees. The disease has been reported in Europe, Oceania, and has recently been found in North America; for this reason, the fungus is considered a potential threat to the reintroduction of the American chestnut.