Symptoms Guide: Acute Decline – AOD Acute Oak Decline

Acute Oak Decline (AOD) is a disease Longitudinal splits Stem cracks affecting several thousand native oak Longitudinal splits form and bleeds trees in Britain. It is considered to have first in the cracks between The bleeding patches occurred in Britain 30-35 years ago. It mainly the bark plates. The usually become visible affects pedunculate oak () and splits are typically 1-2 metres above the sessile oak (Quercus petrea), however other between 5 and 10cm ground and can extend long. They can be close high into the canopy. species of oak can also be affected. to one another In spring, the fluid runs The larval galleries of the buprestid , (10-20cm) or spaced from the splits, down biguttatus, are usually found in association with further apart. the stem and stains the lesions. Various species of bacteria have been bark black. isolated from these lesions. The high co-occurrence of the beetle and the bacteria suggests that these agents play a role in AOD. Dried bleed Lesion under bark At certain times of the Underneath the outer bark at the bleeding point, year the bleeding will the inner bark breaks down creating a lesion, stop, leaving dry, black which develops into a fluid-filled cavity. streaks on the stems. The dried fluid can cake or form a crust around If you think you have spotted this disease the split. in a tree, then report it through the Forestry Commission’s online Tree Alert form: Note: Weeping patches or stem bleeds are a forestry.gov.uk/treealert general symptom or host response to tissue attack from a range of pests and pathogens. A stem Where possible, infected trees should be left in place, bleed alone does not indicate AOD. monitored and cordoned off to prevent access. Where a limited number of trees are infected, it may be prudent to fell and destroy the infected individuals D-shaped holes Tunneling to reduce the risk of infecting nearby healthy trees In approximately Bark removed from trees with symptoms of Acute and to reduce inoculum levels. one third of cases Oak Decline may show signs of tunneling from Minimise the rate of spread by practising ‘D-shaped’ exit holes the larvae of Agrilus biguttatus. good biosecurity. of the beetle Agrilus biguttatus are present Think kit Think transport Think trees in bark plates of affected trees. The Avoid working on or around Avoid taking vehicles and If an infected tree needs to be ‘D-shaped’ exit holes infected trees in wet conditions. machines on to infected sites pruned or felled, strip off the outer are approximately 4mm Clean and disinfect tools and particularly when wet. Wash off bark and the sapwood on site wide and 3mm high. equipment, and wash and dry any build up of soil or organic and burn it. Rapid destruction of ropes before using them to material before leaving site and stripped bark is recommended work on another tree. disinfect any areas that have been to prevent the possibility of in contact with infected material. spreading the disease. For more details, please visit www.forestry.gov.uk/acuteoakdecline