The Royal Horticultural Society has released new guidelines regarding the use of plants which have a risk of being affected by the Xylella fastidiosa bacterium.
It has decided that plants belonging to any of these nine high risk plant groups may only be exhibited at RHS Shows if they are from UK sourced and grown material.
This is defined as those having been propagated from seed in the UK or having been grown in the UK for a minimum of 12 months preceding their use in an RHS Show.
The bacterium Xylella fastidiosa is one of the biggest risks to the UK horticultural industry and the wider landscape.
It infects a wide range of plants including many popular species grown in gardens, such as cherry, hebe, lavender and rosemary. The bacterium causes symptoms including leaf scorch, wilt, dieback and plant death.
Xylella is spread between plants by insects which feed on infected plants and through trade in infected plant material. Xylella is native to the Americas but in 2013, the bacterium was identified as the cause of death of olive trees in Italy.Since then it has been found on a range of ornamental, crop and wild plants in France, Germany and Spain.
The UK government and industry are taking action to prevent the introduction of Xylella and have identified hosts which are considered to present the highest risk of introducing the bacterium into the UK and have also been associated with most outbreaks in continental Europe. These are: Coffea spp. (coffee)
- Hebe spp. (hebe)
- Lavandula spp. (lavender)
- Nerium oleander (oleander)
- Olea europaea (olive)
- Polygala myrtifolia (polygala)
- Prunus spp. (cherry, plum etc.)
- Rosmarinus officinalis (rosemary)
- Spartium junceum (Spanish broom)
The RHS’ plant health team will work closely with exhibitors and the Animal and Plant Health Agency (APHA) to ensure that plants exhibited have been grown and sourced in the UK.
The RHS is also planning to provide workshops for exhibitors on Xylella and other important pests and diseases during the 2018 show season.