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Dothistroma needle blight (Dothistroma septosporum)

Corsican pine infested with Red Band Needle Blight

In Britain, Dothistroma needle blight (DNB), also known as red band needle blight, is caused by the fungus Dothistroma septosporum.  It has been found on a range of conifer species, but pine (Pinus) are by far the most common hosts, with Corsican pine, lodgepole pine and Scots pine all affected. Defoliation can continue year on year and gradually weaken the tree, significantly reducing timber yields. It can also eventually lead to death of the tree.

Symptoms

Trees of all ages can become infected. Symptoms are first seen at the base of the crown on older needles. Infected needles typically develop yellow and tan spots and bands, which soon turn red. Then, as the disease progresses, the ends of the needles turn reddish-brown while the needle base remains green. It is within the red bands that the small, black, spore-containing fruit bodies tend to be found, with symptoms being most apparent in June and July. Spores are released from the fruit bodies during this period, leading to infection of the current year's needles. After this point, the symptomatic needles are shed, and branches can acquire a 'lion's tail' appearance typical of the disease, with only a tuft of the recently infected current year's needles remaining at the branch ends. (See picture below.) This defoliation can continue year on year and gradually weaken the tree, significantly reducing timber yields and causing death of the tree.

Distribution

The disease has been found in most parts of Great Britain. In 2006, 70 per cent of the Corsican pine (Pinus nigra) stands inspected in Britain had the disease, and it is estimated that 44 per cent of these infected stands had crown infection levels greater than 30 per cent. Lodgepole pine (Pinus contorta) and Scots pine (P. sylvestris) are now also being affected. The other main conifers used in British forestry continue to appear to have low susceptibility.

Crown infection of Scots pine seedlings by Dothistroma needle blight

 

 

 

 

 

In 2010, the disease was found infecting pine plants in three forestry nurseries in Scotland. 

Position statement

In 2011 the extent of nursery findings increased, when for the first time our Delamere and Newton nurseries were found to be infected in the same year. 

Spread

Moisture is required for natural dispersal of the fungus, and long-distance dispersal is thought to occur in moist winds and mists. Movement of infected plant material, including infected needles on footwear, clothing, machinery and timber, could also spread the disease.

Action

Management of Dothistroma needle blight is overseen by a Programme Board.  Our research programme includes: disease surveillance; monitoring of the disease’s extent, severity and impact; increasing our understanding of the fungal biology and disease epidemiology; and investigations into potential management strategies.

The GB strategyaddresses the issues posed by DNB. It sets out the current status of the disease, the risks it poses, and actions required to achieve the three key objectives of of the strategy. These are to:

  • maintain pine as a silvicultural option to protect the social, economic and environmental functions of pinewoods, and avoiding impacts of DNB on other conifer species;
  • conserve Great Britain’s iconic Caledonian pinewoods; and
  • reduce collateral damage from other pests and diseases (e.g. bark beetles).

Further information about DNB in Scotland is available from Forestry Commission Scotland.

Movement restrictions

Within the European Union the movement of pine plants intended for planting is regulated though plant passport arrangements. Our plant health authorities inspect growers of pine each year, and only grant authorisation to issue passports if a place of production and its immediate vicinity are free from DNB. Any plants found to have DNB must be destroyed, and authorisation to issue passports will no longer be granted for that place of production.

In exceptional cases authorisation may be granted to move asymptomatic pine (pine plants with no symptoms) to specified regions within Britain where DNB is already present. Growers of pine plants for planting are obliged to inform the relevant plant health authority if they suspect that DNB is present.

There are no movement controls on logs, sawn wood, cut trees (e.g. Christmas trees), branches, foliage or seeds, because these products are not considered a significant pathway for spreading the disease in the natural environment. However, visitors to nurseries should adopt appropriate biosecurity measures to prevent unintentional movement of infected material from the natural environment.

Treatment

Reducing humidity levels can reduce the level of infection, so good weed control is important with young crops, including nursery stock. For older crops, thinning is the main management option available to facilitate air movement and reduce humidity in the canopy. No-thin regimes and delayed first thinning have been shown to lead to significant mortality in public forests managed by us and Natural Resources Wales. 

At present there are no plant protection products with approval that can be used in infected stands in a forest context. However, use of copper-based fungicides is permitted in amenity situations: this can suppress the symptoms, and might be a realistic option for individual or small groups of specimen trees. Fungicides may also be used on nursery stock, Christmas tree farms and amenity crops. 

Research note for more details 

Forestry Commission local contacts for forest managers.

Report a sighting

Findings of DNB in trade, such as in nurseries or garden centres, must be reported to the relevant plant health authority.

  • In England or Wales, please report sightings in trade to the Plant Health & Seeds Inspectorate (PHSI) of the Animal and Plant Health Agency (APHA), tel: 01904 405138;

  • In Scotland, please report findings to the Scottish Government Rural Payments & Inspections Directorate's Horticultural Marketing Unit:  hort.marketing@gov.scot ; 0131 244 6303.

There is no statutory requirement to notify findings in woodland or on other mature trees. Irrespective of this, it is strongly recommended that woodland owners and their agents are made aware of the distribution and severity of DNB on and adjacent to their land so that appropriate management strategies can be put in place as part of their overall risk management.

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Last updated: 21st October 2017