The Possible Role of Armillaria spp. and Phytophthora spp. in the Oak Decline Complex : Disease/Environment Interactions in Forest Decline. Proceedings of a Workshop of the Working Party Disease/Environment Interactions in Forest Decline IUFRO 7.02.06, Vienna, Austria, March 16-21, 1998

1999

S. 49-56

4 Abb., 2 Tab., 16 Lit.

Unselbständiges Werk

200085337

As part of an interdisciplinary research program on oak decline, a detailed survey of the root system of one declining and one healthy-looking oak tree was conducted at two oak stands in eastern Austria. Special attention was directed at partly deteriorated fine-roots and feeder-roots examined for infection by Phytophthora and Armillaria species. Other root samples from two additional healthy and 5 declining oak trees of each site were included in the study to obtain an adequate sample size. Using both selective agar media and apple baiting methods Phytophthora could not be isolated from root samples or from surrounding soil. Armillaria isolates could be identified by the Korhonen intersterility test as Armillaria ostoyae, Armillaria gallica and Armillaria cepistipes. Root infections by Armillaria ostoyae might be a major contributing factor to oak-dieback at Patzmannsdorf. At the "Niederweiden" site low water capacity of sandy chernozems together with changes in groundwater level could contribute to the decline symptoms. Ongoing investigations are also examining the hypothesis that Phytophthora quercina, a newly described species requiring a different siolation technique, is involved in oak dieback at the "Niederweiden" site.