Biosecurity refers to a set of precautions that aim to prevent the introduction and spread of harmful organisms, including non-native pests, such as insects, and disease-causing organisms (known as pathogens), such as some viruses, bacteria, and fungi.

Trees are under increasing pressure from harmful pests and pathogens. There are various factors that can add to this pressure. For example, the increase in global trade and travel provides more entry pathways for pests and pathogens. Additionally, climate change can facilitate a pest or pathogen becoming established in a new environment.

We have seen an increase in spread and detections of new tree pests and diseases in the UK, from the spread of Dutch Elm Disease in the early 1970s, the first discovery of invasive pest Ips typographus (eight toothed bark beetle) in 2018, to the detection of pathogen Phytophthora pluvialis in 2021. Pest and pathogen outbreaks have become more frequent since 2000, compared to the previous 30-year period.

As well as reducing the economic value of trees, these organisms have a wider negative impact on other species, habitats, and ecosystem services.

Carrying out biosecurity measures provides a barrier to the introduction and spread of tree pests and pathogens. The more biosecurity measures we action today, the more resilient woodlands will be to climate change in the future.

1. Understand your site

The key to a healthy, pest or pathogen-free woodland is understanding your site and the threats to it. Make sure you’re ready to tackle any problems by considering the following:

Species composition

Identify the tree species present on your site. This will help focus your efforts on the threats and biosecurity measures most relevant to you.

Potential pest and disease threats

Research which pests and diseases affect the tree species identified on your site – both now and in the future. Find out the risks and statutory obligations for each in case you need to report your findings to the relevant plant health authority.

Potential pathways

Identify the ways (natural or human-made) that tree pests and diseases could enter your site. Consider how the activities on your site could increase the risk.

Potential pathways include:

• moving live plants or plant products
• moving timber and wood packaging, such as pallets
• dirty tools, such as chainsaws, kit, machinery, and vehicles
• contaminated soil and leaf litter
• visitors’ boots, bikes, and other equipment

For example, oak processionary moth can spread naturally through flight but can also be introduced to sites during restocking through the movement of live oak trees. In England, management zones with movement restrictions of large oak trees are in place to help control this.

2. Carry out biosecurity measures

You can significantly reduce the risks to tree health in your woodland by following these three calls to action.

‘Think kit’

• make sure all equipment, including boots, clothing, ropes and saws, is free from soil and organic material before entering and leaving a site
• clean and disinfect chainsaws, pruning saws and other cutting tools as part of routine maintenance, and before using them on a new site

‘Think transport’

• remove any build-up of soil and organic material on vehicles and machinery, including cabs, wheels and footwells, before leaving each site
• use proper off-site wash-down facilities regularly

‘Think trees, plants, and materials’

• responsibly source planting stock through nurseries or suppliers, making sure they meet national standards (such as the Plant Health Management Standard), or have biosecurity policy in place that you trust, by having membership of the Plant Healthy Certification Scheme or a successful Ready to Plant Assessment.
• source planting stock from pest-and-disease-free areas
• keep accurate, up-to-date records of all purchases and supplies that can be traced in the event of an outbreak
• regularly monitor plant and tree stock for signs of ill-health, and report any suspect symptoms using TreeAlert (TreeCheck in Northern Ireland)
• check your plant passport and registration requirements with the Animal and Plant Health Agency (APHA) before importing or moving plants
• source landscaping materials from pest-and-disease-free areas
• be aware of any restrictions, or phytosanitary (plant health) measures and treatments when importing certain materials or their packaging
• request UK or British-grown plants when sourcing planting stock to reduce the risk of accidentally introducing invasive non-native pests and diseases

Whether your land management objectives are economic, environmental or social, reducing the risk of introducing or spreading tree pests and diseases is a high priority. The best way to do this is by following biosecurity best practice.

It is essential that you record any suspicious findings and report these to the relevant plant health authorities. For trees, woodlands and forests, you can report findings to Forest Research via the TreeAlert online portal, or in Northern Ireland use TreeCheck.

To submit a report using TreeAlert you need to provide photographs and other details of the affected tree(s), including symptoms.

If a tree pest or disease is confirmed on the land you own or manage, here’s what you need to know:

Non-notifiable pests and diseases

You don’t need to take any action if the tree pest or disease found on your land is not notifiable. However, to ensure people’s and animals’ safety, and to minimise further spread, we recommend that you:

• continue to implement biosecurity measures
• make visitors aware of the presence of pests and diseases on your land through information boards, posters at entry points, and/or biosecurity guidance on your website
• monitor the trees’ safety as the infection or infestation progresses, and prune or fell affected trees if they threaten to cause damage or injury
• in low-density situations, such as parks or gardens, slow the spread of pests and diseases by removing and disposing of (by burying, composting or, where permitted, burning) infected trees and their fallen leaves and branches

Statutory Plant Health Notices (SPHNs)

If the tree pest or disease is classified as notifiable, you may be issued with a Statutory Plant Health Notice (SPHN) by a statutory plant health authority (such as the Forestry Commission). If so, you must take steps to eradicate or contain the notifiable pest or disease:

• eradicate: you may need to kill the infected or infested trees, such as by felling
• contain: the infected or infested trees may remain standing, but any susceptible material remains on site

If you’re issued with an SPHN, you must follow the instructions provided.

Note: if you receive an SPHN, you are not in any trouble. It doesn’t mean you’ve committed an offence or that you are at fault for the pest or disease being present. However, if you do not comply with the requirements of an SPHN, you may face enforcement action and prosecution.

A list of notifiable pests and diseases can be found on the UK Plant Health Information Portal, under pest and disease factsheets.