During the past decade, and in particular after the wet summer of 2002, an increasing number of trees and stands of European beech (Fagus sylvatica L.) in Bavaria were showing symptoms typical for Phytophthora diseases: small-sized, sparse and often yellowish foliage, a dieback of the crown, and root and coliar rot and aerial bleeding cankers up to stem heights of > 20 m. Between July 2003 and October 2004 109 mature beech stands, among them 93 forests and 16 amenity tree stands, on a broad range of geological substrates were examined for the occurrence of typical Phytophthora symptoms. Coliar rot symptoms were found in 85 stands. In addition, aerial bleeding cankers occurred in 40 stands. In 10 of the 13 stand without stem bark lesions fine root damages and lesions on suberished roots were found. While in most stands trees with stem bark lesions had a scattered or clustered distribution, the majority of trees showed corwn decline symptoms indicating root damages. Isolations for Phytophthora species were carried out in 91 stands. Seven known Phytopthora species and some unidentified Phytophthora isolates were recovered from symptomatic tissues or thizosphere soil of 177 of 233 beech trees (76 %) in 86 stands (95 %). The most frequent species were P. citricola (86 trees in 56 stands) and P. cambivora (71 trees in 41 stands) followed by P. cactorum, P. gonapodyides, P. pseudosyringae, P. syringae and Phytophthora lesions were soon infected by a series of secondary bark pathogens and wood rotting fungi; the predisposed trees were usually attacked by several scale nursery survey in Bavaria demonstrated regular infestations of beech fields with the same range of Phytophthora species as found in the field stands. The results indicate that (i) Phythpthora species may be regularly involved as inciting agents of beech decline, and (ii) planting of infested nursery stock might endanger current and future silvicultural projects aiming on the replacement of pure conifer stands by beech dominated mixed stands.
443.3 (Krankheiten in späteren Wachstumsstadien) 416.3 (An Wurzeln und Stammbasis) 416.4 (An Rinde und Kambium) 176.1 (Dicotyledoneae [Siehe Anhang D]) [430] (Deutschland, 1990-)
