Japanese chestnut gall wasp
|Japanese chestnut gall wasp|
Japanese chestnut gall wasp ( Dryocosmus kuriphilus )
|Yasumatsu , 1951|
The Japanese chestnut gall wasp or chestnut gall wasp for short ( Dryocosmus kuriphilus ) is a representative of the gall wasps (Cynipidae) originally native to South China . Their larvae cause galls on chestnuts ( Castanea ). It is one of the most important pests in chestnut cultivation, especially in China, Japan and partly in the USA . It is considered to be the most important chestnut pest worldwide.
Only female animals are known. The adults are 2.5 to 3 millimeters long and black. Legs, scapus and pedicelli of the antennae , the apex of the clypeus and the mandibles are yellow-brown. The head is finely sculptured. Scutum, mesopleuron, and gaster are smooth and shiny. The propodeum has three separate, longitudinal keels. The propodeum and pronotum are heavily sculptured. The scutum has two pits (notaulices) that approach each other at the rear. The antennas consist of 14 segments, the end segments are not thickened in the shape of a club. The adult animal is similar to the European oak gall wasp ( Dryocosmus cerriphilus ).
The eggs are oval, milky white, 0.1 to 0.2 millimeters long and stalked long. The larvae are 2.5 millimeters long and milky white just before pupation. They don't have eyes or legs. The pupae are 2.5 millimeters long, black or dark brown in color.
Way of life
The chestnut gall wasp forms one generation per year. The reproduction takes place parthenogenetically , males have never been observed.
The adult gall wasps hatch between late May and early July and lay eggs in packets of usually three to five, rarely up to 30 eggs in the leaf and flower buds of the chestnuts. In total, a female lays over 100 eggs and dies after a few days.
The larvae hatch after 30 to 40 days and develop only slowly. They overwinter in the buds of the trees. When the buds begin to emerge in spring, the larvae grow faster. At this time they cause galls on the new shoots. The larvae feed in the bile for the next 20 to 30 days. The larvae pupate between mid-May and mid-July, and the adult females hatch shortly afterwards.
Host plants and harmful effects
Several species of the chestnut genus ( Castanea ) are attacked. The Japanese chestnut ( Castanea crenata ), American chestnut ( Castanea dentata ), Chinese chestnut ( Castanea mollissima ), Castanea seguinii , but also the European sweet chestnut ( Castanea sativa ) are particularly sensitive . Other species and genera are not affected. It affects all ages from the second year.
The galls are 5 to 20 millimeters in size and green to bright pink. Their interior is chambered and usually contains several gall wasp larvae. They prevent normal tissue development. The leaves are crippled and the fruit set is largely prevented. The crop failure can be up to 70%. Whole branches can even die off. In Southeast Asia the harmful effect is less, as there are a number of parasitoids that limit the reproduction of the chestnut gall wasp . However, they are missing in other areas. In Japan the hymenoptera Torymus chinensis is used for biological control of the chestnut gall wasp . Other parasitoids in China are Torymus beneficus , Megastigmus maculipennis , Megastigmus nipponicus and the Ormyrus flavitibialis . In Europe, Japan and the USA, native parasitoids have been found sporadically in chestnut gall wasp galls in these areas, but their potential for controlling chestnut gall wasp is classified as low.
The home range of the chestnut gall wasp is in southern China. It was introduced into Japan around 1940. It probably got to North America and Europe with nursery supplies. It first appeared in North America in 1974. Since it is relatively sensitive to cold, it has remained limited to the southern areas in the USA. In Europe she has been known from Piedmont since 2002 and from Slovenia since 2005. In 2005 the first occurrences were discovered in France ( Saint-Dalmas-Valdéblore , Département Alpes-Maritimes ). There have been EU-wide emergency regulations since 2006, the species is a quarantine organism .
It spreads mainly through the human transport of infected plants or parts of plants (but not the fruits or seeds). The speed of spread of infestation reaches up to 25 kilometers per year. The flight ability is limited, but wind drift is to be assumed.
- Diana Weigerstorfer: Japanese chestnut gall wasp . Forest Protection Info 3/2006 (online)
- EPPO : Data sheets on quarantine pests: Dryocosmus kuriphilus . Bulletin OEPP / EPPO Bulletin, Volume 35, pp. 422–424 (pdf; 58 kB)
- Stephan Hahn: The chestnuts. Food source and threatened natural resource . Book on Demand GmbH, Norderstedt 2004, p. 24f. ISBN 3-8224-2194-4
- Henri Breisch: Châtaignes et marrons. Center technique interprofessionnel des fruits et légumes, Paris 1995, pp. 144f. ISBN 2-87911-050-5
- Faith Campbell: Chestnut Gall Wasp - Dryocosmus kuriphilus Yasumatsu ( Memento of the original from May 9, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . The Global Invasive Species Team ( Memento of the original from May 26, 2008 in the Internet Archive ) Info: The archive link was automatically inserted and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed June 20, 2008.
- Dryocosmus kuriphilus found in the south of France (Alpes-Maritimes) ( Memento of the original from January 5, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF file; 1.2 MB), EPPO Reporting Service, No. 5, May 1, 2007. Accessed June 20, 2008.
- Distribution map ( memento of September 28, 2006 in the Internet Archive ) of the plant protection organization for Europe and the Mediterranean region
- Information from the WSL (PDF file; 327 kB)
- EPPO Workshop on Dryocosmus kuriphilus, Cuneo (IT), 26. – 28. June 2006 , with presentations
- The Japanese chestnut gall wasp (waldwissen.net)