Dendroctonus valens: an invasive forest pest in China
The red turpentine beetle, Dendroctonus valens (Coleoptera: Scolytidae) originating from North America was introduced into China (counties of Yangcheng and Xinshui - Shanxi province) in the early 1980s when unprocessed logs were imported from the USA. In 1999, it was found in Hebei province and by 2003 this bark beetle had spread to 85 counties in 3 provinces of Northern China covering an area of more than 700 000 ha. At present, D. valens has been found in the following provinces: Beijing, Hebei, Henan, Neimenggu (Inner Mongolia), Shaanxi, and Shanxi. It is estimated that D. valens has killed more than 10 million pine trees since its introduction, mainly Pinus tabulaeformis (Chinese red pine), a species which has been widely planted in monoculture during reforestation programmes. The Chinese State Forestry Administration now ranks D. valens as the second most important forest pest nationwide. A national management programme was initiated in 2000 and includes regulatory, sylvicultural, insecticidal, and semiochemical approaches.
In its native range in North America (Canada, Mexico, USA) and parts of Central America (Guatemala, Honduras), D. valens is considered to be a secondary pest of pines (Pinus spp.). It usually infests weakened or dying trees, but outbreaks and tree mortality attributed to D. valens alone are rare. In North America, D. valens can be found on many pine species and occasionally on spruce (Picea spp.) and larch (Larix spp.). In Western North America, P. ponderosa, P. contorta, P. jeffeyi, P. lambertiana, P. monticola and P. radiata are the preferred hosts. In China, the primary host is P. tabulaeformis (P. armandii, P. bungeana and Picea meyeri have occasionally been attacked but there are no confirmed reports of mortality on these species). In Shanxi province, P. sylvestris is a rare non-native species and it has occasionally been attacked by D. valens. As P. sylvestris is more or less continuously distributed across northern Eurasia, this pine species could serve as a potential corridor for the spread of D. valens into Europe.
Several fungal species have been reported in association with D. valens, although their possible role in tree mortality remains to be studied. In China, the most consistently isolated fungus is Leptographium procerum, and studies have indicated that it was most probably introduced into China along with D. valens. The fungi associated with D. valens in China is different to that in the insect’s native range (e.g. Leptographium terebrantis, commonly associated with D. valens in the USA, has not been found in China; L. sinoprocerum is a new species which has been collected from D. valens only in China). Finally, in their review dedicated to D. valens in China, Sun et al. (2014) also stressed that the increasing emergence of new aggressive beetle/fungal associations (e.g. Xyleborus glabratus/Laurel wilt – Platypus quercivorus/Raffaelea quercivora – Pityophthorus juglandis/Thousands cankers disease) raises serious phytosanitary concerns.
The current distribution of D. valens is as follows:
EPPO region: absent.
Asia: China (Beijing, Hebei, Henan, Neimenggu, Shaanxi, Shanxi).
North America: Canada (Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland, Northwest Territories, Nova Scotia, Ontario, Québec), Mexico, USA (Arizona, California, Colorado, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming).
Central America: Guatemala, Honduras.
EPPO note: several American Dendroctonus species attacking conifer trees are already included on the EPPO A1 List (i.e. D.adjunctus, D. brevicomis, D. frontalis, D. ponderosae, D. rufipennis), but D. valens has never been specifically listed.
Gao B, Wen X, Guan H, Knizek M, Zdarek J (2005) Distribution and attack behaviour of the red turpentine beetle, Dendroctonus valens, recently introduced to China. Journal of Forest Science 51(4), 155-160 (abst.).
Bark and Ambrosia beetles of the US ; Canada. Dendroctonus valens. http://www.barkbeetles.info/us_canada_chklist_target_species.php?lookUp=491
Liu ZD, Xu BB, Sun JG (2014) Instar numbers, development, flight period, and fecundity of Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) in China. Annals of the Entomological Society of America 107(1), 152-157.
Sun JH, Lu M, Gillette NE, Wingfield MJ (2013) Red turpentine beetle: innocuous native becomes invasive tree killer in China. Annual Review of Entomology 58, 293-311.
Taerum SJ, Duong TA, de Beer ZW, Gillette N, Sun JH, Owen DR, Wingfield MJ (2013) Large shift in symbiont assemblage in the invasive red turpentine beetle. PLoSONE 8(10), e78126. doi:10.1371/journal.pone.0078126