Widespread Phytophthora infestations of nursery stock in Central Europe as major pathway of Phytophthora diseases of forests and semi-natural ecosystems
Jung, T., Schumacher, J., Leonhard, S., Hartmann, G., Cech, T., Oszako, T., Duda, B., Szkuta, G. and Orlikowski, L.B. (2008) Widespread Phytophthora infestations of nursery stock in Central Europe as major pathway of Phytophthora diseases of forests and semi-natural ecosystems. In: 3rd International Phytophthora and Pythium Workshop: Integration of traditional and modern approaches for investigating the taxonomy and evolution of Phytophthora, Pythium and related genera, 23 - 24, Turin, Italy.
Between 2001 and 2007 extensive nursery surveyes were carried out across Germany, Austria and Poland. In Northern Germany beech, oak and maple fields of 14 nurseries were investigated and 54% were found infested by P. cactorum (23%), P. syringae (23%) and P. cambivora (15%). Other Phytophthora spp. were isolated infrequently. In Lower Saxony, Northwestern Germany beech fields were surveyed in 6 nurseries and 5 were found infested by P. cactorum, P. cambivora, P. citricola, P. gonapodyides (each 2 nurseries) and P. pseudosyringae (1 nursery). In Bavaria, Southern Germany the beech fields of all 9 nurseries tested were infested by a range of 8 Phytophthora species with P. citricola, P. cactorum (each 7 nurseries) and P. cambivora (5 nurseries) being most widespread. In Southern and Western Germany all oak fields (Q. robur, Q. rubra, Q. petraea) of the 8 tested nurseries were infested by Phytophthora spp. P. quercina, P. citricola (each 5 nurseries) and P. cactorum (4 nurseries) were most common. In Poland beech, ash, maple, oak, fir, spruce, pine and larch fields in 40 forest nurseries were tested, and a range of 5 Phytophthora species, mainly P. citricola, P. cactorum and P. cinnamomi, were regularly found in 26 nurseries. Alder fields were investigated in Bavaria, in Eastern Germany, in Poland and in Austria with the specific purpose of detecting P. alni which is responsible for the epidemic alder mortality across Europe. In Bavaria P. alni was recovered from rootstocks of alders from 3 out of 4 nurseries which regularly bought in alder plants for resale, but not in rootstocks from four nurseries that grew their own alders from seed. In addition, P. cambivora, P. cactorum, P. gonapodyides and P. taxon ‘Pgchlamydo’(each 37.5%), P. megasperma (50%) and P. citricola (62.5%) were isolated. In Brandenburg P. alni was found in 5 out of 10 nurseries. In addition, P. cambivora, P. cactorum and P. syringae were recovered. In both countries the infested nurseries used water from infested water courses for irrigation. As a result alders in Bavaria and Brandenburg were produced according to a code of good practice. Control isolations showed that P. alni but not the other Phytophthora spp. could be eliminated. P. alni was also found in several nurseries in Austria and Poland. Extensive field studies in young forest and amenity plantations in Southern and Northwestern Germany, and in more than 3000 alder and more than 200 mature beech, oak, lime and maple stands across Germany demonstrate the ubiquitious involvement of Phytophthora species in the devastating broadleaf tree declines, and the role of infested nursery stock as a major pathway of Phytophthora diseases of trees. The implications of our results for the nursery and the forest industries are discussed.
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