Phytophthora ramorum: update On the impact and wider consequences of the epidemic in Britain

Abstract

Many new Phytophthora pathogens have arrived in the UK via the plant trade in recent decades, but arguably Phytophthora ramorum has been one of the most significant introductions to affect trees. From 2002 onwards during the early stages of the epidemic, the first impacts of P. ramorum were seen in ornamental plant nurseries, then affecting valuable heritage plants in gardens important to the tourist trade, and eventually in broadleaf dominated woodlands (Brasier and others 2004). In the latter, a few tree species, such as European beech (Fagus sylvatica) and sweet chestnut (Castanea sativa), were occasionally affected, although native European oaks proved to be of low susceptibility in contrast to native North American oak species. However, rhododendron, in the form of valued ornamental cultivars in gardens or the invasive non-native shrub Rhododendron ponticum, was the common host across all environments. It also proved essential to the epidemic because it sustained pathogen sporulation, whereas the bole cankered tree hosts did not. As a harmful organism listed within the European Union EC Plant Health Directive (2000/29/EC), phytosanitary measures required eradication or disease containment achieved through the removal of sporulating hosts. Therefore, control measures against P. ramorum focused on rhododendron removal, and the range of tree bole hosts affected fit with the American ‘model,’ with the worst affected species in the Fagaceae family.

Parent Publication

• Proceedings of the sudden oak death sixth science symposium

Citation

Webber, J.F. 2017. Phytophthora ramorum: update On the impact and wider consequences of the epidemic in Britain. In: Frankel, Susan J.; Harrell, Katharine M., tech. coords. Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 4-6.