About chestnut blight
Chestnut blight is a disease caused by a bark-inhabiting fungus (Cryphonectria parasitica), which mostly affects the trunk and branches of host chestnut trees.
The disease invades stems and branches of any size and causes cankers that can grow rapidly. Cankers are dead or malformed areas of bark or woody tissue. In most cases cankers continue to develop until they surround the trunks, stems or branches and the tree eventually dies. Other symptoms of chestnut blight include cracking or peeling bark, trunk and branch swelling, bark and wood degeneration or death, and additional resin exudates.
Under favourable environmental conditions, orange fruiting bodies (stroma) are produced on the outside of the bark inside the canker margins. Spores are formed in stroma, which can spread the disease.
The disease has the potential to spread from cuttings and dead wood for up to nine months.
How does chestnut blight spread?
Chestnut blight can spread via:
- Airborne spores
- Rain splash
- Transport of infected material
- Farm operations e.g. pruning
- Machinery and equipment.
Chestnut blight can also be spread through budding material and cuttings taken from infected trees.
It can also be spread by two types of spores produced in the orange stroma of the fungus:
- One type of spore is ejected from stroma on infected wood and spread by air movement.
- The other spore type is released from infected wood onto the tree surface from where it can be spread by rain splash, water, or any object that comes into contact with it (e.g. clothing, tools or equipment).
Cut branches with the disease are also a serious spreading risk, as the fungus grows more rapidly on dead wood and can produce spores for up to a year after cutting.
Chestnut blight has also been transferred to healthy trees by the use of contaminated cutting equipment such as saws, knives and chainsaws, or tree injection equipment.
Chestnut blight may lie dormant and symptoms may take over a year to develop so, as a precaution, it is important to keep monitoring trees for symptoms.
Can chestnut blight be stopped from spreading?
The best option for containing the disease is to eliminate any sources of infection, including spores of the fungus. This means that infected limbs and tree trunks must be cut off and burnt on site.
New infections cannot be seen until they fully develop and spread onto the bark, so infected tree parts may be missed in an initial pruning. Therefore, pruned trees should be regularly monitored for a reappearance of the disease.
Any destruction and disposal of infected trees must be done under Agriculture Victoria supervision to ensure the highest biosecurity levels of farm hygiene and decontamination are observed.
Is it safe to receive chestnut trees or propagating material?
Chestnut blight is most readily spread through the movement of infected budwood or cuttings. Do not receive any cuttings or new trees unless the source material is from a grove or nursery outside the Restricted Area (see Market access information and material movement restrictions), or from a trusted source within the Restricted Area that has been surveyed and found to be free of the disease.
There are restrictions in place in the Ovens Valley regarding chestnut and oak plant movement. Heavier restrictions are in place in a small area of Eurobin, including machinery and equipment that is used on or been in contact with chestnut or oak trees. Penalties are in place for non-compliance with these restrictions. See Market access information and movement restrictions for further information.