Sweet chestnut blight: what the agencies record

This page reports what the official source says. It is not legal advice: ask the office named here. It lists what the sources record about chestnut blight and does not diagnose any tree. It states a quarantine and reporting rule for Great Britain, so the exact wording is on the Forest Research page linked below. The list of other diseases is on the tree diseases page, and the reporting lines are in the United Kingdom report-a-pest guide.

At a glance

Item	What the sources say
Pathogen	Cryphonectria parasitica, a fungus (an ascomycete) that Forest Research says was formerly known as Endothia parasitica.
Hosts	Sweet chestnut trees in the genus Castanea. Forest Research names European sweet chestnut and American chestnut as the main species at risk. It says oaks are occasionally affected, usually when standing very close to heavily infected chestnuts.
Not a host	Forest Research and the Royal Horticultural Society both say horse chestnut (conker) trees are unrelated and not affected.
Where	North America and continental Europe. Forest Research says it was first confirmed in the United Kingdom in November 2011, in a nut orchard in Warwickshire, England, and has since been found at sites mainly in central and southern England.
Status	Present in the United Kingdom, notifiable and a regulated pest, per Forest Research.
Report to	Great Britain: TreeAlert. Northern Ireland: TreeCheck. Plant traders: the plant health inspector. See the United Kingdom report-a-pest guide.

How the sources say it spreads

Forest Research says long-distance spread can occur through movement of infected sweet chestnut plants, wood or bark in trade, and that the fungus is reported to survive in colonised bark for up to 10 months even if the bark is air dried. It names a small risk of transmission by fruits or seeds. Locally, it says spores move by wind and water and might also be carried by insects and birds, and that wounds made by insects such as the Oriental chestnut gall wasp might help the fungus enter. The Invasive Species Centre says the fungus needs fresh wounds, growth cracks or dead bark to enter, and that spores travel over longer distances on birds. The Royal Horticultural Society says spores are produced in wet weather at any time of the year when temperatures are mild, and that infection starts when spores land on freshly wounded bark.

Forest Research adds that the fungus is reported to live on dead organic matter on broad-leaved trees beyond its parasitic hosts, which lets it persist after infected chestnuts are removed, and that infection can persist on cut timber, branches and woody material.

Symptoms as the sources state them

Bark. Forest Research says all symptoms occur above ground. The bark dies and cracks, and a sunken canker shows where a stem or branch has been girdled. Orange fruiting bodies push through the bark and, in moist weather, release long orange-yellow tendrils of spores. The Invasive Species Centre says reddish-brown cankers on stems of any size can be seen at any time of year, and the bark of a mature canker swells, cracks and eventually falls off.
Leaves. Forest Research says leaves above a girdling canker wilt and turn brown but stay hanging on the tree, while branches below the canker keep healthy foliage. The Invasive Species Centre says some dead leaves may stay on through winter.
New shoots. Forest Research and the Invasive Species Centre both describe new shoots growing below the cankered bark. The Invasive Species Centre says living roots often sprout after infection because the fungus attacks only the above-ground bark.
Time to death. The Royal Horticultural Society says young trees may die within a year of infection, while mature trees may take years. The Invasive Species Centre gives 1 to 3 years in its description of the disease.
Season. The sources give no season in which symptoms first appear. They describe symptoms as visible through the year.

Look-alikes and reporting

The Invasive Species Centre says American chestnut is often confused with horse chestnut, chestnut oak, chinkapin oak and beech. Forest Research asks that suspected cases be reported through TreeAlert or TreeCheck, which both require clear, well-lit close-up photographs of the symptoms.

What the agencies publish for control

Forest Research says where findings are confirmed, infection is managed through statutory measures for eradication and containment. It says the Forestry Commission serves Statutory Plant Health Notices on owners of affected sites that set out biosecurity measures, which can include removal and destruction of all sweet chestnut trees, with movement restrictions set site by site. It lists reporting suspected findings, not moving infected plants, bark or wood, and washing and disinfecting tools, vehicles, equipment and footwear after visits to infected sites as the measures for limiting spread. It records a demarcated area in Devon announced on March 26, 2026 and in force from April 2, 2026. The Royal Horticultural Society says there is no chemical control available to gardeners and that suspected cases should go to the plant health authority. Who may apply pesticides is covered on the pesticide licences page.

Regulation in Great Britain

Forest Research says Cryphonectria parasitica is a regulated pest in the United Kingdom, with restrictions on imports of sweet chestnut plants, wood and bark from all third countries, and that UK plant passports are required for moving Castanea plants with bark and isolated bark. For moving wood in general, see moving wood and firewood. A related oak disease is on the oak wilt page.

Credit

The Forest Research material was read under the Open Government Licence v3.0 and is restated here in our own words.