@article {EPP:EPP2243, title = {Phytophthora ramorum and Phytophthora kernoviae on naturally infected asymptomatic foliage}, journal = {EPPO Bulletin}, volume = {39}, number = {1}, year = {2009}, pages = {105{\textendash}111}, publisher = {Blackwell Publishing Ltd}, abstract = {

Phytophthora ramorum and Phytophthora kernoviae are recently discovered invasive Phytophthoras causing leaf necrosis and shoot tip dieback mostly on ornamental and forest understorey species, but also cause bleeding cankers on stems of a wide range of tree species. Sporulation occurs only on infected shoots or fruits and foliage so foliar hosts are central to the disease epidemiology. In field trials to assess infection in trap plants exposed to natural inoculum of P. ramorum and P. kernoviae on rhododendron in south west England, it was discovered that leaves of the trap plants (Rhododendron {\textquoteleft}Cunninghams White{\textquoteright}) and holm oak (Quercus ilex) were asymptomatically infected and supported sporulation of both pathogens. More than half the rhododendron trap plants exposed to inoculum of P. kernoviae became infected compared with approximately a third of those exposed to P. ramorum in a natural situation. Approximately one third of the infections were detected from asymptomatic foliage for both pathogens. The significance of these findings for plant health regulation based on visual inspection as a measure to prevent introduction and dissemination of both these pathogens is explored and research gaps identified.

}, issn = {1365-2338}, doi = {10.1111/j.1365-2338.2009.02243.x}, url = {http://dx.doi.org/10.1111/j.1365-2338.2009.02243.x}, author = {Denman, S. and Kirk, S.A. and Moralejo, E. and Webber, JF} } @article {PPA:PPA1243, title = {In vitro leaf inoculation studies as an indication of tree foliage susceptibility to Phytophthora ramorum in the UK}, journal = {Plant Pathology}, volume = {54}, number = {4}, year = {2005}, pages = {512{\textendash}521}, publisher = {Blackwell Science Ltd}, abstract = {

Leaves of 11 coniferous and 23 broad-leaved tree species important to UK forestry were tested for their susceptibility to the quarantine pathogen Phytophthora ramorum using a detached leaf assay. Two European and two USA isolates were used. Wounded and unwounded leaves were dipped in zoospore suspensions during summer; conifers were also tested in winter. Successful infection of tissue and amount of necrosis were assessed. Highly susceptible broad-leaved hosts included Aesculus hippocastanum, Fraxinus excelsior, Quercus ilex, Ulmus procera and, to a lesser extent, Castanea sativa, Q. cerris and Q. petraea, together with Umbellularia californica and rhododendrons. Acer pseudoplatanus, Alnus glutinosa, Carpinus betulus, Corylus avellana, Fagus sylvatica, Prunus avium, Q. robur, Q. rubra and Q. suber showed consistently low susceptibility. Conifer species including Abies procera, Picea abies, P. sitchensis, Pseudotsuga menziesii, Sequoia sempervirens and Tsuga heterophylla were also susceptible. Pseudotsuga menziesii and A. procera were severely affected. Pinus contorta, P. nigra var. maritima and P. sylvestris were virtually resistant, while Taxus baccata was only slightly affected. Increased necrosis was apparent on leaves that were wounded prior to inoculation. These results extend the known range of trees that P. ramorum is able to attack and confirm its relative host-nonspecificity.

}, keywords = {broad-leaved species, conifers, detached leaf dip assay, foliage, forest species, Sudden oak death}, issn = {1365-3059}, doi = {10.1111/j.1365-3059.2005.01243.x}, url = {http://dx.doi.org/10.1111/j.1365-3059.2005.01243.x}, author = {Denman, S. and Kirk, S.A. and C.M. Brasier and Webber, JF} }