Phytophthora species involved in the decline of Fagus sylvatica (beech)
In the past decade, an increasing number of Fagus sylvatica trees and stands have been showing symptoms of Phytophthora diseases both in Europe (e.g. in Italy, Germany, Sweden, UK) and USA. Affected trees may show abnormally small and yellowish foliage, crown dieback, bark necroses, collar rot, bleeding cankers, fine root destruction, and may eventually die. Large scale studies were done in Europe and USA, and showed that several Phytophthora species are associated with declining F. sylvatica.
- In USA, the pathogen found on declining F. sylvatica was tentatively identified as P. inflata*.
- In Bayern (Germany), 6 different Phytophthora species were recorded. P. citricola was most frequently found, followed by P. cambivora and P. cactorum. P. gonapodyoides, P. syringae, P. pseudosyringae and an unidentified Phytophthora isolate were each isolated from a few trees. In Northern Germany, earlier studies showed that P. cambivora was predominant, while P. gonapodyoides and P. pseudosyringae were isolated infrequently.
- In UK, studies done in 1938 had showed that P. cambivora and P. syringae were recorded from root and collar rot of F. sylvatica in several forests. More recent studies showed that P. ramorum and P. kernoviae were responsible for bleeding cankers of F. sylvatica trees growing in the vicinity of infected Rhododendron.
- In Switzerland, P. citricola and P. cactorum were recovered from the rhizosphere of a declining tree.
- In southern and central Italy, P. pseudosyringae and P. cactorum were isolated from necrotic bark lesions.
- Finally in Turkey, another study showed that P. cambivora was isolated from necrotic collar tissues of F. sylvatica subsp. orientalis.
* Note: P. inflata was described by Caroselli and Tucker (1949) causing cankers on Ulmus americana and U. fulva in Michigan (US). Since then, it has rarely been found. It was once reported in England (Hall et al., 1992) from rotting roots of Sambucus tenuifolium and Syringa vulgaris grown in a nursery in Suffolk. Very recently, it was isolated from a Rhododendron ponticum showing wilting foliage and blackened shoot tips in a nursery in Scotland (Schlenzig, 2005). In an adjoining nursery, P. inflata was also isolated from a Gaultheria shalon and a Vaccinium vitis-idaea plant with leaf lesions and dieback symptoms. Its pathogenicity was confirmed on Rhododendron and Gaultheria (not yet on Vaccinium).
Caroselli NE, Tucker CM (1949) Pit canker of elm. Phytopathology 39, 481-488.
Hall G, Dobson S, Nicholls C (1992) First record of Phytophthora inflata in the United Kingdom. Plant Pathology 41, 95-97.
Schlenzig A (2005) First report of Phytophthora inflata on nursery plants of Rhododendron spp. Gaultheria shalon and Vaccinium vitis-idaea in Scotland. Plant Pathology 54, p 582.
Jung T, Hudler GW, Jensen-Stacy SL, Griffiths HM, Fleischmann F, Osswald W (2005) Involvement of Phytophthora species in the decline of European beech in Europe and the USA. Mycologist, 19(4), 159-166.