Becki Cadd, Biosecurity and Awareness Manager at the Forestry Commission, shares how ten years on, the ‘Keep it Clean’ tree health campaign continues to help protect our woodlands and forests from pests and diseases.
This year marks 10 years of the Forestry Commission’s Keep it Clean campaign. A decade of encouraging simple, evidence-based actions that help slow the potential spread of harmful tree pests and diseases across our woodlands and forests.
What began as a practical reminder to remove soil and leaf litter from boots and equipment, has grown into a nationally recognised initiative supporting the long-term resilience of our treescapes. As we mark this milestone, we are working on refreshing our campaign to enable everyone who enjoys the outdoors to help reduce the spread of pests and diseases.
10 years of Keep it Clean campaign gold logo. A decade of impact underpinned by scienceThe Keep it Clean campaign is built on strong scientific evidence, including reports focusing on a range of boot cleaning measures to protect natural vegetation and assessing the spread of Phytophthora species.
What is Phytophthora?Phytophthora (pronounced fy-TOFF-thora) is a group of microscopic, fungus like organisms called oomycetes. Even though they look and behave like fungi, they are more closely related to algae.
Phytophthora is behind some of the most damaging tree and plant diseases worldwide. These include Ramorum disease in Britain, sudden oak death in the US and Kauri dieback in New Zealand.
Through water and contaminated soil, even tiny quantities carried on boots, bike tyres, dog paws or tools can move the pathogen from one woodland to another.
Phytophthora ramorum symptoms on larch. 6 key facts about Phytophthora Phytophthora produces microscopic spores called zoospores with tail like structures that help them move. They swim through thin layers of water in the soil, a bit like tiny tadpoles, allowing them to travel quickly. Some species can survive in soil and organic material long after it appears dry, even after the original host plant or tree has died or been removed. Only a small amount of contaminated material is enough to establish disease in a new location. More than 150 species are currently known, with new species emerging as global trade and environmental pressures evolve. A Phytophthora species caused the Irish potato famine. This demonstrates how profoundly these organisms can shape landscapes and societies. Phytophthora ramorum foliage infection. Credit: Forest Research How humans can spread pathogensPhytophthora is a significant concern, but it is not the only organism that threatens trees and plants. Human activity can also spread other pests and pathogens, including:
emerald ash borer (Agrilus planipennis) – an invasive beetle causing severe ash death rates in North America and parts of Europe, spread partly via infested firewood and timber oak processionary moth (Thaumetopoea processionea) – introduced to the UK through the movement of infested plants, and a public health hazard due to its irritating hairs canker stain of plane (Ceratocystis platani) – not currently in the UK, but highly destructive in continental Europe and spread easily through contaminated tools and machineryThese risks underline the need for simple actions that reduce the spread of pests and diseases.
Keep it Clean has been designed to turn these insights into practical steps for both professionals and the public to follow. As a result, good biosecurity practice is being increasingly embedded across forestry, arboriculture, conservation and wider land based sectors.
Phytophthora ramorum felling site. Why biosecurity mattersA key challenge is that many harmful organisms travel in small amounts of soil and organic debris picked up during everyday visits. Soil and water borne pathogens such as Phytophthora can survive for long periods, even after the soil appears dry. This means that activities which move soil, such as walking, cycling, forestry work or dog‑walking, can unintentionally transport pathogens into new areas.1
What research tells usOne of the most detailed UK studies on this issue was carried out by Forest Research in 2018 – 'Biosecurity engagement with hikers at Rowardennan'. After reviewing 28 international studies, researchers concluded that recreationists, including hikers, can be instrumental in spreading pests, pathogens, invasive species and weed seeds through their outdoor activities. Unintentional pathogen dispersal by visitors is also likely.2
Further evidence comes from the Plant Health Centre funded study ‘Assessing the spread of Phytophthoras’. Using molecular testing, researchers detected Phytophthora ramorum DNA on soil collected from boot treads and bike tyres in forests such as Kirroughtree and Glentrool, where Ramorum disease was present on larch.
Researchers concluded that Phytophthora species can be picked up and transported on boots, bike tyres and harvesting machinery, enabling their spread into new areas.3
The study recommended that recreational forests display clear biosecurity messages, encouraging visitors to clean boots and bike tyres before and after every visit.
The evidence is clearSoil movement is one of the most significant pathways for spreading harmful tree pathogens, and visitors can unintentionally contribute to that spread.
That’s why simple cleaning habits matter. By reducing the amount of soil we move between places, we help slow pathogen spread and give our forests a better chance to recover, adapt and remain resilient in a changing climate.
Phytophthora ramorum bark infection. Credit: Forest Research Small actions, big impactBiosecurity does not require specialist knowledge or complex equipment. It’s about taking a moment to care. Cleaning off visible soil between visits is a practical step that greatly reduces the risk of moving harmful organisms. When these habits become routine, the collective effect across millions of visits is profound.
Practical biosecurity stepsResearch shows that even basic cleaning can significantly reduce the likelihood of transporting pathogens.4
By taking a few simple actions between visits, you can help reduce the spread of pests and diseases by:
using a stiff brush and water, remove all soil and organic material from boots, bike tyres, tools and equipment until they are visibly clean encouraging others to take similar precautions when out and about sharing the Keep it Clean campaign with others to help spread the wordWherever possible, carry out cleaning on a hard surface such as paving or gravel, rather than near streams, rivers or drains. When muddy water is allowed to dry on a hard surface, it removes the moisture and organic material that many pests and diseases need to survive.
Just as taking litter home has become second nature, it’s important that everyday biosecurity becomes a normal part of enjoying our woodlands and forests.
Biosecurity boot cleaning. Strengthening resilience for the next decadeAs we mark 10 years of Keep it Clean, we thank everyone who has contributed, including partners, industry professionals, volunteers, walkers, cyclists and families.
The relaunch of the Keep it Clean campaign is planned for the autumn and supports wider plant health and resilience plans. By continuing to act on the evidence and working collaboratively, we can strengthen the resilience of our woodlands and forests for future generations.
Read more on how to prevent the introduction and spread of tree pests and diseases, and watch our video on cleaning your walking shoes for biosecurity.
Biosecurity engagement with hikers, 2019 ↩︎Biosecurity engagement with hikers, 2019 ↩︎Assessing the spread of Phytophthoras, 2024 ↩︎The efficacy of boot cleaning measures to protect natural vegetation, 2023 ↩︎ seen at 09:59, 11 May in Forestry Commission.