A critical element of arb training for many is knowing the best means of limiting the spread of Chalara, the fungal disease that already besets so many of our ash trees and is tipped to ultimately infect most of the country’s ash tree population, akin to the notorious 1970s Dutch Elm Disease.
The importance of minimising Chalara’s spread cannot be underestimated. The risk of the transmission of spores via infected leaves means that one must always try to guard against new areas becoming infected through the adoption of sensible biosecurity precautions.
The fungus that causes the disease, Chalara fraxinea, is capable of surviving up to a year of frost or leaf degradation, but cannot fruit if buried. Although it can be killed in some cases by the heat that composting generates, this cannot be guaranteed and it is unlikely that sufficient heat to kill the spores is generated by the smaller scale heaps seen in parks and gardens.
Recipients of our Staffordshire arborist training working on any site should always heed any requirements outlined in statutory Plant Health Notices over more general advice. Nonetheless, those intending to fell or prune infected trees are advised to wait – if possible – until leaf fall before doing so.
Infected leaves may not need to be removed at all in some circumstances – it is widely advised to leave infected mature ash trees, for example, in place. The fungus in the ash tree leaves that causes the disease is able to be spread by airborne pathways or by physical movement through human agents. It is the movement of infected material, such as plants and leaves, that generally causes the spread of Chalara into new areas.
As a general rule, the smaller the volumes of leaves being transported and the shorter the distance they are being transported, the lower the probability of the spread of the disease. If leaves that have been affected by the disease do need to be disposed of, the emphasis should be on using on-site disposal options available on or near an infected area, thereby minimising the risk of infection spreading to other areas.
Those benefitting from our arboricultural training in Staffordshire should also be aware of the low risk status of timber/cordwood that means there is no control over its movement at this time. Measures should also be taken by those that have just worked on infected trees and are set to move into other areas with no or minimal signs of infection, to remove leaves and rachis from vehicle tyres, chippers and payload.
The other pests and diseases that can be present nearby only makes the adoption of biosecurity measures all the more sensible for those enrolling in arb training in Staffordshire like that of Ian Morgan Arb.