Phony peach: the next disease after Chalara threatening to devastate Britain’s trees, and also plants.
Xylella fastidiosa has wreaked havoc in the US and Europe and could dwarf the impact of ash dieback in the UK, where at Ashridge the ash trees have so far shown considerable resistance to Chalara.
Defra were found wanting some ten years ago for not imposing restrictions to prevent Chalara entering the Country because of E U implications – so what hope is there for stopping Phony Peach.
With experts warning that it could make the devastating ash dieback disease seem like “a walk in the park”, the UK is on red alert for signs that Xylella fastidiosa has entered the country.
First confirmed in Europe three years ago when it ran rampant across olive plantations in southern Italy, a subspecies of Xylella has since been detected in southern France, where it has destroyed vines and lavender plants, and in Corsica. Xylella fastidiosa has also been found in both South and North America where it is commonly referred to as “phony peach disease” and where it has caused severe damage to citrus and coffee plantations. In New Jersey it has attacked more than a third of the state’s urban trees.
According to guidance issued by the Department for Environment, Food and Rural Affairs (Defra), Xylella has already infected oak and maple trees, hebe, lavender and rosemary. It results in multiple symptoms, including wilting, diebacks, stunted growth and leaf scorches.
Raoul Curtis-Machin, head of horticulture at the Horticultural Trades Association, the body representing the UK’s growers and landscapers, said it had initially been thought that Xylella could not survive in the UK because of the climate.
“But last autumn the Animal and Plant Agency discovered a new strain, which is cold-hardy, in Corsica and France,” Curtis-Machin said. “It’s getting very close to Britain. What has alarmed us is that it’s quite difficult to spot and it affects a massive list of different host plants. The list has got so big that the EU has stopped publishing a printed list and just publishes it online. Unlike many plant diseases Xylella has the potential to affect multiple species, rather like the way human flu viruses can mutate.”
Horticultural experts have been lobbying hard for the EU to extend plant passport regulations, which currently apply only to wholesale importers. “But that’s only one chunk of a huge trade,” Curtis-Machin said. “There are a lot of garden designers going over to Italy and importing big olive trees. God knows what’s on them. You may not see the symptoms and a year later it could be hopping out on to the plane trees, and before you know it you’ve got the trees in the avenues of The Mall dying off.”
An outbreak in the UK would result in the introduction of stringent emergency control measures. All known host plants within half a mile of the outbreak would be destroyed. Sweeping restrictions on the movement of plants within a buffer radius of six miles of the outbreak would be imposed for five years.
This could have potentially devastating consequences for urban landscape gardeners. For example, an outbreak on a landscape site in Canary Wharf, east London, could result in the near shutdown of landscaping work in the capital.
The HTA says it alerted the government to the risk of importing ash dieback in 2009 without much success. To combat another disease taking hold, the association is trying to convince Defra and other agencies of the need to develop a secure market for UK-grown trees.
Despite pledges to improve the amount of woodland cover and tree planting in the UK, the amount of new planting in England has dropped from eight thousand acres in 2013-14 to six thousand acres in 2014-15. Experts believe the yet-to-be published figure for 2015-16 could be as low as four thousand acres.
“Trees have a stabilising effect on the climate,” Curtis-Machin said. “Trees absorb air pollution. You’ve got horrific levels of air pollution outside schools right now in a lot of our urban areas. As we’ve seen with the recent flooding, without trees water catchment is shot to pieces. We know that trees stabilise banks, so without them you end up with a lot more landslips and you get a lot more road closures.”
A bleak outlook for conservationists if Phony Peach arrives.
Thanks to Jamie Doward for his contribution