This webpage only offers guidance on how to manage extensive stem bleeding on oak (the condition that might be caused by bacteria).
Recommended course of action
Our understanding of the exact cause of this condition is limited at present so it is difficult to make fully informed recommendations about the management of affected trees. Until better information is available the following course of action is recommended:
- Record the number and location (preferably using 10 point GPS readings) of symptomatic trees and the severity of their condition. Severity can be indicated by the number and size of bleeding patches on the stem, the distance between bleeding patches and the condition of the tree canopy (crown density).
- Record the distribution of the symptomatic trees relative to site features (e.g. low-lying territory, slope, water courses, roads, public access points etc.).
- Unless there is immediate concern about safety, infected trees should be left in place and monitored. If possible cordon the trees off to prevent access to them. It is unknown how the causal agents spread, but several potential agents have been found in the bleeds pouring from the trees so this could be a source of infection. Therefore minimise contact with bleeds to reduce the possibility of transfer from tree to tree.
- If however only a limited number of trees appear to be infected on a site and most are of the same oak species, it may be prudent to fell and destroy the infected individuals to reduce the risk of infecting healthy trees and to keep inoculum levels low.
- Never use parts of infected trees (leaves, bark, wood) for mulch or compost.
- Inform the public about the condition of the oaks by erecting information notices about the condition at various access points to the woodland - example of notice that could be used.
- Pruning infected trees is discouraged as it may increase the risk of disease spread and weaken the tree by reducing its capacity to contain or overcome the bacterial infection, and also make it more susceptible to secondary infections.
Recommended precautions when felling symptomatic trees
- Avoid felling when conditions or trees are wet as this may increase the chances of spreading the pathogen(s).
- If trees are heavily infected and dying or dead and need to be felled, the ideal solution would be to strip off the outer bark and the sapwood on site after felling and burn it. Rapid destruction of stripped bark is recommended to prevent the possibility of spreading the disease.
- It is recommended that barked trees, logs or branches are not moved off site.
- Planking logs can be undertaken on site to facilitate removal of the bark (and sapwood), but caution should be exercised about the use of the wood because it is not known if the disease affects timber properties.
- It is unknown whether or if so for how long the causal agents survive in the wood but it seems reasonable to expect that following kiln-drying to below 20% moisture content, preferably using a high temperature treatment protocol, bacteria would be unlikely to survive.
- Felling or pruning equipment must be disinfected after use. Also consider brushing mud and debris off soles of boots and spraying boots and vehicle tyres with disinfectant before leaving the site (see table below).
- Until more is known about the condition and which oak species are susceptible, avoid replanting the entire site with the same oak species as the diseased ones. The risk could be reduced by only replanting with mixtures of species including no more than 25% of the susceptible species.
- It is unknown whether young nursery trees can be infected with the disease and as yet there is no evidence of this occurring in Britain. However, as a precaution be wary of collecting and planting acorns or young trees from infected sites. Be especially cautious about using planting material from infected sites for plantings elsewhere.
- Do not transfer felled symptomatic trees to newly planted sites as a natural source of deadwood habitat.
|Disinfectant||Concentration||Exposure time||Healthy and safety|
|Virkon||5%||Spray and allow to dry||Virkon material data sheet (PDF-28K)|
|Ethanol or industrial methylated spirits (methanol)||70%||Spray and allow to dry||Ethanol and ethyl alcohol material data sheet|
|LYSOL® spray||Undiluted||Spray and allow to dry||LYSOL® spray material data sheet (PDF-46K)|
Note: all disinfectants should be used in accordance with the recommended safety precautions (refer to the material safety data sheet for each product).