Symptoms

You may see the following symptoms:

Chronic oak decline

  • Mainly affects pedunculate oak (Quercus robur)
  • Progressive deterioration of the crown, taking many years or even decades
  • Deterioration begins with leaves becoming paler and smaller
  • Twigs start to dieback, followed by small branches
  • The dieback may progress to large branches, and in the most severe cases the tree dies
  • Others may recover partially or stabilise, although the problem may begin again at a later date
  • Recovering trees often have a healthy-looking lower crown, but with large dead branches in the upper crown projecting above the green lower canopy like antlers (known as a ‘staghead’ effect)

Acute oak decline

  • Mainly affects mature (greater than 50 years old) trees of pedunculate oak, sessile oak (Quercus petraea) and hybrids between the two, although some younger trees have been affected and occasionally also other Quercus species
  • A dark fluid weeps down the trunk from cracks (about 5-10cm long) in the bark. This may stop and dry out at certain times of year, and can be washed off by heavy rain
  • Multiple bleeding patches may be present, from close to ground level to high in the canopy
  • Some affected trees have died within four to five years
  • Unlike chronic oak decline, symptoms of deterioration in the crown may not appear until just before the tree dies

 

 

 

Control

 

Non-chemical control

  • Aim to achieve healthy, vigorous growth by matching the tree to its site (soil conditions, climate, etc.)
  • Evidence suggests that trees derived from those of local provenance are best adapted to the local conditions and more likely to resist pest and disease attack
  • The presence of large numbers of oak trees with extensive bleeding should be reported to the Tree Health Diagnostic Advisory Service of Forest Research (part of the Forestry Commission) (see the link below) – this will help in their investigation of the problem. Acute oak decline is not a notifiable disease, however, and there is no legal requirement to report cases
  • Current advice is to leave affected trees in situ (unless there is an immediate concern about safety) and to monitor them
  • However, if only a few trees are affected, amongst a large number of healthy trees of the same species, it may be prudent to fell them
  • Pruning of affected trees is not recommended, unless dead branches pose an immediate health and safety risk
  • Do not compost any part of an infected tree, nor use any resulting wood chips as a mulch or soil conditioner