Assessment of potential economic and environmental impacts caused by Phytophthora ramorum in Europe

Economic and environmental impacts of Phytophthora ramorum in Europe were evaluated within the European Union framework 6 project on “Risk Analysis for P. ramorum a pathogen threat to Europe” (RAPRA). Impact assessment was conducted according to three different scenarios: 1. “Nursery System” - describes losses occurring in nurseries where special growing conditions and trade with plant material influence spread and dimension of the disease, 2. “Northern European Tree Host System” - based on observations in the United Kingdom, the Netherlands and Germany where infections of trees (beech, red oak) at forest or park sites only occur, when Rhododendron as a foliage host is present to a certain extent and 3. “Southern European Tree Host System” where a potential foliage host is Quercus ilex growing as an understory plant in combination with susceptible tree hosts. Taking climatic conditions favourable for the pathogen, distribution of host plants and pathogen distribution into account, the present economic and environmental impact in Europe is minimal to moderate. Potential impacts depend on the host system: for nurseries, facing higher costs for hygiene measures, treatments of plant material and trade impacts, no changes are expected in the future as long as basic conditions like plant health regulations are not altered noticeable. In the “Northern European Tree Host System” present impacts are moderate and restricted to few areas where Rhododendron are associated with tree hosts and environmental impact is caused. The potential impact is expected to be not more than moderate as long as no widely distributed foliar hosts of Northern European forests occur. In the “Southern European Tree Host System” present impacts are minimal since the pathogen does not occur in the environment. But here potential impact is assumed major if P. ramorum would be introduced and spread in the unique Mediterranean laurel and Q. ilex forests.