Biosecurity measures for tree works on a development site

Biosecurity turns up in arboricultural conditions because a development site is one of the easiest ways to move a tree pest from one place to another. Chippers, saws, boots, soil on tyres, arisings used as mulch and imported nursery stock all carry material between trees. Where a council conditions an arboricultural method statement, expect it to require biosecurity measures, and expect the discharge submission to be rejected if that section is two generic sentences.

The measures themselves cost little and take minutes. What costs money is finding out, three years after handover, that the semi mature limes you imported brought something with them and the landscape condition now cannot be signed off.

Why it appears in conditions at all

Two strands meet. The first is plant health law. The Animal and Plant Health Agency and the Forestry Commission operate statutory controls on notifiable pests and diseases, with powers to serve notices requiring destruction, removal or restriction of movement. Oak processionary moth, the larger eight toothed European spruce bark beetle, Asian longhorn beetle, sweet chestnut blight and several Phytophthora species all carry reporting duties, and some are subject to designated or demarcated areas where movement of host material is restricted.

The second is the landscape condition on your own permission. Replacement planting has to establish, and BS 8545 on trees from nursery to independence, together with BS 5837:2012 for the construction phase, set the expectations a council draws on. A planting scheme that fails because the stock arrived diseased is a breach of condition, and the developer carries it.

So the biosecurity section is not paperwork for its own sake. It is the part of the method statement that protects both the retained trees and the aftercare obligation.

Tool and machinery hygiene

The working rule is that anything that cuts, chips or digs is a vector. Practical measures that a method statement can commit to and a site manager can actually deliver:

• clean saw chains, blades and pruning tools of sap and sawdust before moving between trees, and disinfect where a tree is suspected of infection
• keep a dedicated set of tools for any tree under suspicion, and work on it last in the day
• brush down chipper chutes and blowers at the end of each operation rather than at the end of the week
• wash down plant tyres and tracks before leaving a site with a known problem, at a designated point shown on the tree protection plan
• provide a boot brush and disinfectant station at the site entrance where Phytophthora is a live risk, and require its use in wet weather
• avoid pruning susceptible species in wet or humid conditions, which is when spore movement is most effective

Name the disinfectant type, the dilution and who checks it. A condition discharge officer reads that as evidence the measures are real.

Moving soil, arisings and mulch

This is where most avoidable spread happens on construction sites.

Soil moves pathogens, particularly the water moulds. Topsoil stripped from near an infected tree should not be spread across a planting area, and imported topsoil should come with a source and a specification. Where a tree has been felled under a statutory plant health notice, the notice will usually dictate what happens to the timber and brash, and that overrides your site preference.

Arisings are a judgement call. Chipping on site and leaving material within the same area is normally lower risk than carting it off, because you are not introducing anything new. The exception is chipping diseased material and then using it as mulch beneath susceptible species, which concentrates inoculum exactly where you do not want it. Ash affected by ash dieback is a safety question rather than a movement question in most cases, because the pathogen is already widespread, but brittle timber changes how the work is done.

Timber from oak, sweet chestnut, spruce and pine deserves particular care because of the beetle and canker risks attached to those genera. Where a demarcated area applies, movement of host material off site may require a plant passport or be prohibited outright. Check before the grab lorry is booked.

Sourcing and quarantining new stock

The highest risk event on most schemes is the arrival of the landscape planting. Semi mature trees imported from continental nurseries have repeatedly been the route by which new pests have entered the country.

What to specify:

1. Stock grown in the UK or Ireland, with the nursery named and the growing period stated, rather than simply supplied from a UK depot.
2. Supply from a nursery holding recognised plant health accreditation, and plant passports for species where they are required.
3. Smaller stock sizes where the design allows, because young transplants establish better and carry less risk than heavy semi mature trees.
4. A holding or quarantine area on site, separated from retained trees, where new stock is inspected on arrival and held for a defined period before planting.
5. Rejection criteria, so the site team knows it can turn a delivery away.
6. A record of every delivery: species, supplier, passport reference, date.

Specify stock sizes and provenance in the planting schedule rather than leaving it to the contractor, and keep it consistent with the tree planting conditions the authority has imposed.

Notifiable pests and how to report

If site operatives find something that looks like a notifiable pest, the reporting route matters more than the identification. Tree pests and diseases in the wider environment are reported to the Forestry Commission, including through its online reporting tool, and the Animal and Plant Health Agency deals with plant health notices and imported material. Oak processionary moth nests must be handled by trained operatives with appropriate protective equipment, because the caterpillar hairs are a health hazard as well as a tree health one.

Put the reporting route, with the named responsible person on site, in the method statement. Then the answer to a suspicious finding is a phone call rather than a week of internal discussion while the chipper keeps running.

Work involving protected trees adds a layer. Felling or pruning a tree covered by a Tree Preservation Order, or in a conservation area, needs consent or notice in the normal way, and a plant health problem does not remove that requirement unless the work is urgently necessary to remove a danger, in which case the exemption is narrow and needs evidence. Where a felling licence is in play the position is different again, as the interaction between woodland orders and felling licences shows.

Recording measures on site

Keep it simple and auditable: a biosecurity page in the site diary, dated toolbox talk records, photographs of the wash down point and quarantine area in use, delivery records with passport references, and a short note of any suspected pest and what was done. That file is what discharges the condition, and it takes a site manager a few minutes a week.

Wording a condition can secure

Councils rarely draft biosecurity wording well, so it is worth offering it. Something in this shape works:

No tree works, site clearance or planting shall take place other than in accordance with the approved arboricultural method statement, which shall include biosecurity measures covering tool and machinery hygiene, the handling and disposal of arisings and soil, the sourcing, inspection and quarantine of new planting stock, and the route for reporting suspected notifiable pests and diseases. Records shall be kept and made available to the local planning authority on request.

That is enforceable, it does not commit the authority to policing a specification it cannot inspect, and it lets you discharge the condition with a document you already have. Pair it with the BS 5837 survey and the Landscape Strategy so that the retained trees and the new planting are dealt with in one submission, which is the fastest way to discharge a tree protection condition.

Draft the arboricultural and landscape documents for your scheme on PlanScope, then have an arboriculturist complete the method statement and sign it off.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Arboricultural work of this kind should be prepared or checked by a suitably qualified arboriculturist, and this is general guidance rather than legal advice.