Introduction of Dryocosmus kuriphilus into Piemonte, Italy: Addition to the EPPO Alert List
In spring 2002, in the south of Cuneo (Piemonte, Italy), a sample of Castanea showing unusual swollen buds was sent by a grower to the regional phytosanitary service. Examination revealed the presence of Dryocosmus kuriphilus (Hymenoptera: Cynipidae), a species originating from China, which is considered as one of the most serious pest of Castanea. This insect has been introduced into Japan (in 1941), Korea (in 1963) and into the south-east of USA (in 1974) where it caused serious damage to Castanea plantations (as these were mainly planted with susceptible Chinese and Japanese cultivars). Losses of up to 60-80% of chestnut production have been observed, as well as tree mortality.
In Italy, it is suspected that the insect was introduced on planting material as eggs or first larval instars inside asymptomatic buds. The presence of D. kuriphilus was recorded in a few places in the communes of Boves, Peveragno, Robilante, Chiusa Pesio and Borgo San Dalmazzo, on Euro-Japanese hybrids of chestnut (Castanea crenata x C. sativa). The severity of the attack was high on some hybrid cultivars, but less severe on European chestnuts (although a few trees showed some damage). In Italy, phytosanitary inspections are being made in nurseries to avoid commercialization of infested plants, information is being sent to chestnut growers, and surveys are being done to delimitate the area of infestation. So far, the insect has not been found outside Piemonte. This information was presented to the EPPO Panel on Phytosanitary Measures which felt that this new dangerous pest of chestnut should be added to the EPPO Alert List. The information which has been used for the Alert List essentially came from a datasheet drafted by Dr Vettorazo, Servizi Fitosanitario, Regione Veneto) and a PRA report prepared by Dr Bosio (Settore Fitosanitario, Regione Piemonte) for the EPPO Panels on Phytosanitary Measures and on Quarantine Pests for Forestry.
Dryocosmus kuriphilus (Hymenoptera: Cynipidae – Oriental chestnut gall wasp)
Why: Considering the recent introduction of Dryocosmus kuriphilus, a serious pest of chestnut, into Europe (Piemonte, Italy), the EPPO Panel on Phytosanitary Measures considered that it should be added to the EPPO Alert List.
EPPO region: Italy (Piemonte region, South of Cuneo province).
Asia: China, Korea, Japan.
America: USA (south east: Alabama, Georgia, North Carolina and Tennessee).
On which plants: Dryocosmus kuriphilus attacks Castanea crenata (Japanese chestnut), C. dentata (American chestnut), C. mollissima (Chinese chestnut), C. sativa (European chestnut) and their hybrids. This species also infests C. seguinii in China, but not yet other wild North American species of Castanea: C. pumila and C. alnifolia, which are very often grown adjacent to infested chestnuts.
Damage: D. kuriphilus is a univoltine species with female populations reproducing by parthenogenesis. Females lay eggs inside buds. Early instar larvae overwinter inside buds. At the time of bud burst in spring, their presence induce the formation of a 5-20 mm diameter green or rose-coloured galls. Larvae feed inside these galls and adult wasps emerge in summer. By attacking vegetative buds and forming a gall, D. kuriphilus disrupts the twig growth and reduce fruiting. Yield reductions of up to 60-80% have been observed. Severe infestations may result in the decline and death of chestnut trees. D. kuriphilus is considered in the areas where it is present, as the most severe pest of chestnut.
Dissemination: D. kuriphilus can be spread over long distances by movements of infested twigs or shoots and young plants. Natural spread is also ensured by flying adult females.
Pathway: Plants for planting, cut branches, shoots, buds of Castanea from countries where D. kuriphilus occurs.
Possible risks: C. sativa is widely spread in the EPPO region in forests and plantations for wood and fruit production. D. kuriphilus is considered as the most serious pest of chestnut worldwide. It is very likely to be able to establish in many EPPO countries particularly in the centre and south where cultivated or wild chestnuts grow. Spread of the pest from the infested area in south Piemonte is very likely by females flying and movement of infested young chestnut plants and grafts. Detection and control of the pest is difficult (hidden mode of life). Transfer of the pest from infested areas in Asia and America to EPPO countries may occur, on limited scale, by introduction of infested grafting materials with eggs or first instar larvae inside the buds.
EPPO RS 2003/061
Panel review date - Entry date 2003-05
Draft EPPO Data Sheets. Dryocosmus kuriphilus, drafted by Dr Vettorazzo, 2003.
EPPO document. PRA for Dryocosmus kuriphilus by Dr. Bosio, 2003.
Bosio, G., Brussino, G.; Baudino, M. ; Giordano, R. ; Ramello, F. (2003) Una nuova minaccia per la castanicoltura piemontese. In provincia di Cuneo si sta diffondendo uno degli insectti più nocivi per il castagno. Quaderni della Regione Piemonte, Agricoltura no. 35, 24-25.
Available on Internet: http://www.regione.piemonte.it/agri/ita/news/pubblic/quaderni/corrente/dwd/35_pag_24_25.pdf
Melika, G.; Brussino, G.; Bosio, G.; Csóka, G. (2003) [Chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu 1951 – Hymnoptera: Cynipidae), a new pest of chestnuts in Europe]. Növényvédelem, 39(2), 59-63.
Web site of the Regione Piemonte – Montagna et Foreste.
Un nuovo pericoloso parassita del castano: il cinipide galligeno Dryocosmus kuriphilus Yasumatsu by G. Bosio and G. Brussino. http://www.regione.piemonte.it/montagna/foreste/cinipide.htm