Preventing pandemics in plants

Strict new import regulations have been introduced for plant hosts of high-risk pests; including favourites such as lavender, rosemary and olive

Pandemics don't just affect people. Sadly there are now a number of serious plant health threats that are spreading rapidly across many countries. We need to do everything possible to keep them out of the UK.

The Department for Environment, Food and Rural Affairs (Defra) has introduced tighter controls as of 21 April 2020 on plants for planting which are hosts of high-impact pests and diseases.

However, on 5 June, the European Commission concluded that Defra’s new regulations for Xylella and plane canker were disproportionate and “not supported by the most recent scientific justification.” Defra does not agree with this conclusion (see Defra update) and encourages “stakeholders and industry to employ risk management practices which maintain the robust protection and assurance that the Defra regulations provide.”

What can people in the UK do?
The public have a critical role in keeping pests and diseases such as Xylella out of the UK:

1. Don’t bring back plants and plant products from abroad – do not bring back plants (including seeds and cuttings) from abroad. Commercial importation of plants requires a combination of inspection, notification and documentation checks designed to reduce the risk of infected plants entering the UK. 

2. Buy plants sourced and grown in the UK from reputable nurseries - If a plant is UK sourced and grown (or raised from seed here in the UK) it poses a low risk; Xylella has not been detected in the UK and is not seed-transmitted. If you are unsure about the origin of plants at garden centres and nurseries, check with staff for clarification, and seek out suppliers that stock UK-raised plants.

3. Be aware of the symptoms caused by Xylella – we should all be aware of the variety of symptoms Xylella causes, and which plant species it can attack. 

4. If you see unusual symptoms report your suspicions – if you suspect Xylella could be in your garden or local area, do not attempt to control the disease yourself. Collect together available information including the host plant, symptoms, origin, and import history and report your suspicions to the plant health authorities.

Key priorities for improving the UK’s plant biosecurity


Xylella symptoms. Image courtesy of Penn State Department of Plant Pathology and Environmental Microbiology ArchivesXylella fastidiosa

Xylella fastidiosa is one of the most damaging pathogens worldwide. Xylella has wreaked havoc on olive plantations in parts of Italy and is now causing damage in France, Portugal and Spain.

The bacterium has a large host range and is spread easily via insect vectors. Xylella is not in the UK, but there is a significant risk of the bacterium being imported via infected plant material being moved within the EU and from third countries.

Defra’s stringent new regulations for Xylella fastidiosa apply to imports of coffee, polygala, olive, almond, oleander, lavender and rosemary.

Tough new import requirements for olives, lavenders and rosemary

Olive, oleander, lavender, rosemary and almond plants may only be imported if the National Plant Protection Organisation (NPPO; Defra’s equivalent in the exporting country) certifies that:

  • The plants for planting have been grown in a place of production registered and supervised by the NPPO;
  • The place of production and surrounding 200m have been demonstrated to be free from Xylella fastidiosa based on official inspection and testing for at least 1 year prior to export;
  • The place of production has been officially inspected at times when Xylella  symptoms are most likely to be visible, and sampling and testing has been done on plants due to be exported, according to international standards;
  • Just prior to export, the plants have been officially inspected and tested if suspect Xylella symptoms are observed (again according to international standards); and
  • For oleander, lavender and rosemary, additional requirements for controlling insect vector populations must be implemented

In areas where Xylella is known to occur, plants must be grown under complete physical protection to exclude insect vectors with appropriate hygiene measures to ensure that Xylella is not transmitted by tools or equipment.

Under the new regulations imports of coffee and Polygala myrtifolia plants are completely prohibited from both EU and non-EU countries.

In response to these new regulations, RHS Head of Horticultural Relations, Chris Moncrieff, said: “This year there will be little effect as all the young plants will have been imported and grown on for sale in spring/summer of 2020. It will be next year’s season that will be more problematic, but I suspect that if there is resource and facilities available, young plant producers will build up their supply of stock plants in these species to be able to provide UK-grown material as starter plugs in 2021 as there will be a brilliant demand for these products.”

He also pointed out there are already UK growers seeking an opportunity here: 

“From a nursery’s point of view it could be seen as a big problem, but for the more enlightened growers such as Vitacress Ltd, a herb grower who switched into lavender and rosemary a year ago, it’s a real opportunity to substitute imports.”

The RHS is part of the BRIGIT consortium which aims to build the UK’s capability to prevent establishment of vector-borne plant pathogens (such as Xylella) and to increase our preparedness to respond should they be introduced.

Emerald ash borer

The emerald ash borer (EAB), Agrilus planipennis is a highly destructive wood-boring beetle that feeds on the phloem of ash trees.
New regulations for EAB apply to Fraxinus sp., Juglans ailantifolia, Juglans mandshurica, Ulmus davidiana and Pterocarya rhoifolia. Current EU regulations for Fraxinus, Juglans and Ulmus mean that imports of species in these genera are prohibited from all third countries pending a risk assessment. The new EAB regulations will become applicable if the current EU regulations are lifted.
The new EAB regulations state that plants for planting, other than fruit, and seed but including cut branches with leaves, must be accompanied by a Phytosanitary Certificate which includes an official statement that they originate in an area free from EAB and not within 100km of a known outbreak area.
These regulations currently apply to plants for planting originating in the following countries, Belarus, Canada, China, North & South Korea, Japan, Kazakhstan, Mongolia, Russia, Taiwan, Ukraine and the USA.

Ceratocystis platani (Canker stain of plane)

Ceratocystis platani is an aggressive fungal pathogen that attacks plane trees by entering through wounds and causing canker stain disease and tree death.
The EU regulations implemented on 14 December 2019 revoke the UK Protected Zone status for Ceratocystis platani.  Under the new Defra regulations, the UK reverts back to being a Protected Zone for this pest. Imported plane trees must now be grown throughout their life in a pest free area or EU Protected Zone for Ceratocystis platani.
The requirements apply to imports from Albania, Armenia, Switzerland, Turkey, the USA and the EU. An official statement must confirm this requirement.

Candidatus Phytoplasma ulmi (Elm yellows phytoplasma)

Defra are correcting an error by the European Commission, whereby import and movement requirements were inadvertently omitted from the EU Plant Health Regulation concerning the UK Candidatus Phytoplasma ulmi (elm yellows) Protected Zone.
Plants for planting of Ulmus (other than seeds), must be from a place of production where no symptoms of the pathogen have been observed, including in the immediate vicinity, since the beginning of the last cycle of vegetation. The requirements apply to imports to the UK from third countries and all EU countries and the requirements must be confirmed by an official statement from the NPPO.

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