Alien plants spreading disease

PUBLISHED: 13:30 08 July 2008 | UPDATED: 22:02 15 June 2010

Alien pests and diseases inadvertently imported on exotic plants are threatening the plants in our gardens and across the countryside, according to a report launched today (July 8).

Alien pests and diseases inadvertently imported on exotic plants are threatening the plants in our gardens and across the countryside, according to a report launched today (Tuesday 8th July) by a scientific working group led by the Royal Horticultural Society (RHS). The number of plant disease outbreaks is up by 60% on last year*. Increased global plant trade, coupled with evidence of rapid climate change, suggests that the problem will multiply.Recent Defra reports have highlighted the worrying spread of disease on rhododendrons in the south west of England caused by Phytophthora ramorum and Phytophthora kernoviae, while many other diseases, including Cylindrocladium buxicola, [box blight] which is responsible for the destruction of native box hedges, and Ophiostoma novo-ulmi, [Dutch elm disease] are well known to the working group.The report, Non-native diseases and the future of UK gardens, is being published today. It proposes that the horticultural industry worldwide develops effective systems to manage the risks that growing and trading of ornamental plants are now creating. Suggested features of such a system would be similar to those, driven by the supermarkets, that are now familiar in relation to food assurance schemes. The report suggests that new quality assurance systems, driven by a voluntary code of conduct, could sit alongside the current UK plant inspection programme and offer further reassurances to the plant buying public. In 2005, £870 million was spent on imported plants by the British public, three times as much as in 1988. The current inspection scheme only applies to plants known to play host to diseases and does not provide the opportunity to capture evidence of new diseases symptoms throughout the plant production, transportation and selling process. Dr Simon Thornton Wood, Director of Science and Learning at the RHS, explains, "The current plant inspection programme works exceptionally well for diseases we already know about. But it is the unknown diseases on plants that would not normally be considered problematic that are the real cause for concern. Phytophthora kernoviae and P. ramorum entered the UK because they were not known about and so not checked for. They have wreaked havoc with cultivated rhododendrons and now threaten to spread to our native heath land. "However, an industry code of conduct could provide the answer, with every stage of the production and transport process managed with disease risk in mind. We would then be able to avoid another situation like sudden oak death or Dutch elm disease that has changed the face of the Britain's countryside.Striking the balance between plant health and providing the variety of plants that inspire this nation of gardeners, is at the forefront of the RHS' mind. The UK's leading gardening charity believes that consumer awareness could be the key to ensuring that a code of conduct, underpinning true quality assurance, is developed by the plant importing trade. Dr Simon Thornton Wood continues, "Working together gardeners can help the RHS to track the emergence and spread of pest and disease problems and together we can all take responsibility for the health of our gardens and the wider environment. Everyone has an interest in ensuring that high-quality, disease-free plants arrive at our shores and reach our gardens.

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