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Chalara dieback of ash - management of ash leaves and saplings

 Advice for householders, landowners and local authorities.

Ash dieback disease (Chalara fraxinea) - leaf dessication, wilting and blackening caused by infection, contrasted with healthy ash leavesThis advice supports the Chalara Control Plan and biosecurity measures to prevent or slow down the spread of the disease.  As far as possible it  accommodates existing waste management practices to minimise any disruption to local authority operations in particular. The advice follows consultation with the Environment Agency, the Food and Environment Research Agency (Fera), the Forestry Commission and others. Any requirements in statutory Plant Health Notices take precedence over this general advice. 

In many circumstances there might be no need to remove infected leaves. Infected mature ash trees should be left in place.

This advice applies only when someone intends to move infected leaves as waste. The disease is caused by a fungus in the ash tree leaves which can be spread by airborne pathways or by physical movement. The main means of spread into new areas is by movement of infected material (plants and  leaves). The shorter distance that leaves are transported and the smaller the volumes being transported, the less likelihood there is of the  disease being spread.

Where leaves affected by the disease require disposal, the preferred way to reduce the rate of spread of the infection is by using on-site disposal options available on or near an infected area which will destroy the spores.

Gardeners should not collect dead leaf litter from elsewhere, or use it as compost. Spores can be transmitted via infected dead leaves and this could infect new areas.

The fungus which causes Chalara can survive frost or leaf degradation for up to a year, but it is unable to fruit if it’s buried under the soil, and the heat generated by composting might well kill it, although this is uncertain. Evidence on this is still emerging, so a precautionary approach is recommended. Defra continues to work  to gain a better understanding of the disease, which might lead to changes in disposal advice.

Although there are confirmed finds of Chalara there are no officially designated infected areas at present. Certain areas, such as East Anglia and Kent, show clusters of outbreaks where infection is higher than in areas where isolated findings have been detected. It is likely that further infected sites will be detected in addition to those already identified. Local authorities and others might wish to follow this advice irrespective of whether they are in an area which has had a confirmed finding.

Infected areas

Depending on the nature and location of any infected vegetation the following options are suggested in decreasing order of preference.

(a) Burning on site on the ground or in mobile incinerators brought to site (where these are used because they offer a practical solution to deal with a high volume of leaves) where allowed under legislation on smoke control areas, and subject to the potential risk of smoke nuisance. The best way to do this is for householders, farmers and landowners to be considerate by advising their nearest neighbours before lighting a bonfire, so that they can be prepared for any minor inconveniences which might arise.

(b) Burial in the ground by local authorities would constitute a landfill operation and requires an environmental permit which fulfils the requirements of the Landfill Directive. For this reason local burial may not be a practicable option. However, individuals acting in a private capacity are not subject to the same requirements so householders may bury affected leaves within the grounds of their premises if they wish.

(c) Composting on site. There is no clear scientific evidence available on the effectiveness of composting as a treatment. Composting is less effective when leaves are collected into smaller heaps, as in parks and gardens, because temperatures in small heaps are too low to kill spores. However, in these situations, covering the leaves with a 10cm layer of soil or 15-30cm layer of other plant material, and leaving the heaps undisturbed for a year (other than covering with more material) is likely to prevent any spore dispersal. Any leaves which are not destroyed or otherwise processed (e.g. through composting) can be used for mulching or on allotments only in areas where the disease is already present. Given the uncertainties mentioned above, wherever possible any resulting compost should be spread on or near the infected source and not passed on to third parties who might transport it considerable distances for spreading elsewhere. 

(d) Incineration or landfill off-site. Moving infected ash leaves for purposes other than destruction should be avoided where possible. Where it is not possible to deal with leaves from affected areas on site, the waste should be securely contained either by bagging or in closed containers. Leaves should be transported the shortest distance possible for incineration (including energy recovery) or non-hazardous landfill at existing permitted facilities.

(e) Composting or other biological treatment off-site. Off-site composting and other biological treatment remains a less preferred option because of uncertainty over conditions for destruction of the fungus. If the compost is used locally, this would reduce any possible residual risk. Although gully ‘emptyings’ and dedicated street sweepings, as normally collected, will contain some leaf litter, these wastes should not be taken to biological treatment facilities which produce quality compost for agricultural use, irrespective of whether the sweepings may be affected by the Chalara fungus. This is due to contamination of road sweepings, and is outlined in  existing Environment Agency guidance. As with any waste, its movement should be accompanied by a written description of the waste which will enable others to comply with the Duty of Care under s.34 of the Environmental Protection Act 1990, and the waste only be transported to a facility which is authorised to receive it. Where a consignment of waste comes from a source and is highly likely to contain waste infected with Chalara, that fact should be recorded on any waste transfer note to assist others handling or processing the waste. The Environment Agency has published a regulatory position statement which will allow the disposal of infected trees and plants without an environment permit.

Non-infected areas

The spread of Chalara is not evenly distributed around the country. Where there is no suspicion that trees or leaves are infected with Chalara and there is no need to remove the leaves, they can be left where they fall. Where leaves need to be removed, e.g. as part of normal maintenance, existing waste management arrangements may continue to be used.

Local authorities in particular should be vigilant for the incidence of Chalara in their areas and, if in any doubt, take a precautionary approach with any green waste which they collect. Gully emptyings and street sweepings, as normally collected, should not be taken to composting facilities which produce quality compost. Composting-related research is being considered in line with the needs of Chalara Management Plan and end-users and will be carried out with the involvement of a number of organisations including local authorities. These should be able to go ahead in non-infected areas using dedicated collection rounds to collect leaf litter.

Green waste collected from the public

Local authorities should advise householders not to put out green waste suspected of being affected by Chalara, but to deal with it within the grounds of their own premises, in all but exceptional cases. Where it is suspected that collected green waste is affected, local authorities may choose to continue sending this for composting nearby, although this is a less preferred option if the compost is known to be intended for use at distant locations. Local authorities are encouraged to discuss this with their contractors. Local authorities should prioritise incineration with energy recovery or landfill at an existing permitted site, where these are available nearby. Where there is a high degree of confidence that the green waste collected will not be affected by Chalara or is to be transported and processed for use locally, local authorities should continue with their existing arrangements, but remain vigilant as to the spread of the disease.

Regulations and permits

Any organisation or business carrying out the recovery or disposal of waste may only do so with the benefit of an environmental permit or by having registered a relevant exemption from the need for a permit. Local authorities, farmers and others should take advice from the Environment Agency.  There is an exemption from the need for an environmental permit for burning waste in the open (known as D7), provided that the total quantity of waste burned over any period of 24 hours does not exceed 10 tonnes at the site. There are other exemptions for the burning of waste as a fuel in a small appliance (U4) and for burning waste in an incinerator with a capacity of less than 50kg an hour.

Larger composting operations need an environmental permit. There is an exemption from the need for an environmental permit for the aerobic composting and associated prior treatment (known as T23) where the quantity of waste stored or treated does not exceed 80 tonnes at any time where the operation takes place at the place where the waste is produced, or 60 tonnes if the treated waste is to be removed elsewhere. Permitting controls do not apply to individuals acting in their own private capacity.

Waste burial is a landfill operation. Local authorities, farmers and other businesses require an environmental permit to bury waste. An environmental permit for the burial of waste will be subject to the controls of the Landfill Directive. Waste burial is therefore unlikely to be a viable option for infected ash tree waste. There is an exemption from permitting for the deposit of agricultural waste in piles of up to 250 tonnes where trees are required to be felled under a Statutory Plant Health Notice.

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Last updated: 1st February 2016