Dothistroma needle 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 Dothistroma needle blight and does not diagnose any tree. Forest Research describes findings in trade, such as nurseries and garden centres, as reportable to the plant health authority, and says there is no statutory requirement to notify findings in woodland or on other mature trees. 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	Dothistroma septosporum, a fungus. Forest Research says it is also known as red band needle blight, and Utah State University Extension gives the cause as Mycosphaerella pini. Forest Research names a related species, Dothistroma pini, as not thought to be present in the United Kingdom.
Hosts	Mostly pines. Forest Research says it has been found in the United Kingdom on Corsican, lodgepole, Scots, ponderosa and bishop pine, with larches, firs, hemlocks, spruces and Douglas fir appearing to have low susceptibility. Utah State University Extension names Austrian and ponderosa pine as the most susceptible.
Where	The Woodland Trust says across the United Kingdom. Utah State University Extension says widespread in forests in western North America.
Status in the United Kingdom	Present. Forest Research says it is reportable in trade and that foresters are trained to recognise it, so it does not ask the public to report suspected cases in forests.
Report to	England and Wales: the Plant Health and Seeds Inspectorate. Scotland: the Scottish Government Horticulture and Marketing Unit. Northern Ireland: the DAERA Plant Health Inspection Branch. See the United Kingdom guide.

How the sources say it spreads

Forest Research says the fungus needs moisture to spread naturally and that long-distance dispersal is thought to happen in moist winds and mists. It adds that infected needles on footwear, clothing, machinery and timber could carry the disease. It describes spores landing on a susceptible host, germinating on the needle surface and growing in through the stomata, with late spring to late summer the likely critical period and severe episodes linked to wet springs. It says infected first-year and second-year needles stay on the tree and are the main source of spores the following spring and summer. The Woodland Trust says it most likely spread through transport of infected plant material and by wind over land. Utah State University Extension says the fungus does most damage on trees planted outside their natural range, and that a toxin it releases causes the red color in needles.

Symptoms as the sources state them

September. Forest Research says in Britain the first symptoms are visible on infected needles from September, usually on older needles: yellow and tan spots and bands that turn red.
June and July. Forest Research and the Woodland Trust both say symptoms are most apparent in these months. Forest Research says needle tips turn reddish-brown while the base stays green, and small black fruit bodies show within the red bands.
After that. Infected needles are shed, and branches take on a "lion's tail" look with only a tuft of the year's needles at the end. Forest Research says this can repeat year after year and gradually weaken the tree.
Not always banded. Forest Research and the Woodland Trust both say the red banding is not always evident and the needle may be brown or reddish overall.
Timing of infection. Utah State University Extension says first-year needles are typically infected from mid-summer, older needles from May to October, and that the interval from infection to symptoms ranges from four weeks to six months.

Look-alikes and lab confirmation

Forest Research says the overall brown or reddish needle color can easily be confused with symptoms of other needle diseases. Utah State University Extension names brown spot needle blight, caused by another Mycosphaerella species, as a very similar disease. It says symptomatic plants can be sampled and checked for the fungus, and that a sample can go to its diagnostic laboratory through a county Extension agent.

What the agencies publish for management

Forest Research says that where the disease has been costly, control has centred on fungicide, but that the focus in the United Kingdom is resistant species and good stand management, including thinning pine stands to improve air circulation in the crowns. It says no plant protection products are approved for infected forest stands and that copper-based fungicides are permitted in amenity situations. The Woodland Trust says the main concern is the effect on Scotland's Caledonian pine forests, and that native Scots pine withstands low levels of infection. Utah State University Extension lists pruning lower branches, adequate tree spacing and clearing debris as cultural measures. Who may apply pesticides is covered on the pesticide licences page.

Credit

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