Widespread Phytophthora Infestations of Nurseries in Germany and Austria and Their Role as Primary Pathway of Phytophthora Diseases of Trees

Albany

2009

S. 140-141

Artikel aus einer ZeitschriftUnselbständiges Werk

200156121

Between 2001 and 2007 extensive nursery surveys were carried out across Germany and Austria. In Northern Germany beech, oak and maple fields of 14 nurseries were investigated and 54 percentwere found infested by P. cactorum (23 percent), P. syringae (23 percent) and P. cambivora (15 percent). Other Phytophthora spp. were isolated infrequently. In Lower Saxony, Northwestern Germany beech fields were surveyed in six nurseries and five were found infested by P. cactorum, P. cambivora, P. citricola, P. goapodyides (each two nurseries) and P. pseudosyringae (one nursery). In Bavaria, Southern Germany the beech fields of all nine nurseries tested were infested by a range of eight Phytophthora species with P. citricola, P. cactorum (each seven nurseries) and P. cambivora (five nurseries) being most widespread. In Southern and Western Germany all oak fields (Q. robur, Q. rubra, Q. petraea) of the eight tested nurseries were infested by Phytophthora spp. P. quercina, P. citricola (each five nurseries) and P. cactorum (four nurseries) were most common. Alder fields were investigated in Bavaria, Southern Germany, in Brandenburg, Eastern Germany 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 three out of four 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 percent), P. megasperma (50 percent) and P. citricola (62.5 percent) were isolated. In Brandenburg P. alni was found in five out of ten nurseries. In addition, P. cambivora, P. cactorum and P. syringae were recovered with annually changing isolation frequencies. In both countries the infested nurseries used water from infested water courses for irrigation. In Austria P. alni was found in one of the four nurseries studied. 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. 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 and oak stands across Germany demonstrate the ubiquitous involvement of Phytophthora species in the devastatingbroadleaf tree declines, and the role of infested nursery stock as a primary pathway of Phytophthora diseases of trees. The implications of our results for the nursery and the forest industries are discussed.