Estimating the Susceptibility to Phytophthora alni Globally Using Both Statistical Analyses and Expert Knowledge
Phytophthora alni is a recently hybridized soil and waterborne pathogen causing root and collar rot of species of the genus Alnus (alder). It has quickly spread throughout Europe via planting of infested nursery stock and irrigating fields with infested river water. Once introduced, the pathogen spreads naturally with streams, floods, and other drainage water. P. alni can also be passively transported with the bare-root nursery stock, as it is able to adhere to and infect fine roots of visually symptomless plants of alder and other tree species exposed to the pathogen.
We used a classification tree on 434 infested and healthy sample points to determine the required conditions for P. alni to successfully infest a nonflooded forest site. Sample points had been collected from 2003 through 2006, and a potential distribution surface was created for forested areas in Bavaria. A tenfold cross validation accuracy of 78 percent was attained. To understand the potential hazard posed by P. alni elsewhere in the world, the rules from the Bavarian classification tree were applied along with additional expert knowledge in a multicriteria model to create a global susceptibility surface for P. alni.
- Introduction : Phytophthora alni is a host-specific, highly aggressive soil and waterborne pathogen, which causes root and collar rot of Alnus (alder) species.
- Methods : Between the spring of 2003 and the winter of 2006, a total of 307 P. alni infested and 127 healthy/noninfested alder tree locations were sampled in forested areas in Bavaria.
- Results : Seven terminal end nodes were used and accounted for 78.34 percent of the variability.
- Discussion : The original Bavarian classification tree identified five ecological factors important in the distribution of P. alni. Where these factors occur together in the environment, the likelihood of infection is increased.
Encyclopedia ID: p3328
