Plant Health
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Plant Health |
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HomepagePlants and SeedsPlant HealthPests and diseasesPhytophthora ramorum | |||
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Phytophthora ramorum Surveys and Research |
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Update
on Surveys In addition to the ongoing survey of commercial nurseries and garden centres, inspections have been extended to 14 known outbreak sites and to 51 established plantings of Rhododendron and Viburnum to determine if P.ramorum has spread from nurseries. Since 1 April 2002, over 6500 inspections have been made at over 3000 premises. Currently, P.ramorum has been found at over 130 sites in England and Wales, as well as over 20 sites in Scotland and the Channel Isles. This total includes 6 findings on established plants growing outside in the soil. In addition to Rhododendron and Viburnum, there have now been two findings on Pieris and one finding on Camellia. So far there have been no findings on oak or any other trees. We continue to take eradication action against any findings of the disease, including findings on established plants growing outside in soil. This action is being taken on a precautionary basis because of the widespread and serious damage to a range of trees, which is being caused by this disease in parts of the USA. In addition it is planned in 2003 to conduct a small survey of Vaccinium in view of findings of P.ramorum on Vaccinium species in the USA and in Poland. Update on scientific developments The Plant Health Division of Defra, in partnership with the Forestry Commission and the Horticultural Development Council is currently funding a programme of scientific research to assess the threat posed by P. ramorum to the UK horticultural industry and the environment as a whole. We have jointly committed substantial resources to support the current work to investigate key biological aspects of the organism including development, dispersal and survival under a range of environmental conditions, as well as determining the range of tree, heathland and ornamental species at risk. Investment has been made in improved methodology for detection and identification of P. ramorum in plant material, soil and water as well as an evaluation of potential control methods. This has primarily been done through diversion of resources from other areas of work and demonstrates the importance that has been attached to this disease. The results from this research will help to put forward effective eradication and control measures based on a sound understanding of the disease. This collaborative programme will help speed up the process of understanding the disease and how it can be controlled. The range of ornamental, heathland and tree species which are hosts of P. ramorum are currently being determined. Whereas ornamentals are important in the introduction and spread of the pathogen, hedgerow and woodland under-storey species represent potentially important sources of inoculum for possible epidemics in trees. Over sixty species have been tested in leaf bioassays in the laboratory: nine species were potentially highly susceptible (e.g. Rhododendron, including R.ponticum, Camellia, Leucothoe, Pieris, Sambucus and Eucalyptus); nine were potentially moderately susceptible (e.g. Symphoricarpus, Arctostaphylos, Fuchsia, Photinia, Ulmus, Viburnum); twelve were potentially slightly susceptible; and 29 were potentially resistant or immune. In these studies, there was little indication that the non-tree host range and pathogenicity of American and European isolates differed significantly. Hedgerow and under-storey species found to be susceptible to the disease in the laboratory were ash, wych elm, elder, sycamore, honeysuckle, ivy, dog-rose and Rhododendron ponticum. However, caution should be taken when extrapolating laboratory tests on wounded leaves to a natural situation. To date only Rhododendron, Viburnum, Pieris, Camellia, Kalmia, Syringa, Leucothoe and yew have been found infected in the UK, all infected plants were present in nurseries or managed gardens. If you can't find the information you need in these pages please Contact us. |
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| Page last modified: 29 July 2003 Page published: 21 July 2003 |
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