New modelling shows land‑manager actions could slow the spread of emerald ash borer if it reaches Great Britain

Ash trees in Great Britain are already under severe pressure from ash dieback, a disease expected to cost the UK up to £15 billion over the next 100 years. The emerald ash borer (EAB), an invasive beetle responsible for the death of millions of trees across North America and parts of Eastern Europe, represents a second threat to ash trees in Great Britain. New research by scientists at Rothamsted Research, the University of Warwick, Forest Research, and the Stockholm Environment Institute, University of York shows that the ability to slow or contain this pest will depend not only on biological factors but also on the responses of different types of land managers across Great Britain.

“We know from North America that emerald ash borer is exceptionally hard to manage once established,” said Dr Vasthi Alonso Chávez, “Our work shows that the way that land managers inspect, report and act on invasive threats has a very important role to play in tree health surveillance strategies.”

What the study found

The study combines a biological model of emerald ash borer (EAB) arrival and spread with a dynamic model of land managers’ decision making based on interviews, workshops and survey responses from more than 400 stakeholders. The study investigates how different forms of surveillance and management might influence the course of an EAB invasion in three contrasting landscapes of Great Britain: Kent, Suffolk and North Wales.

Using simulations, the researchers evaluated how EAB might be detected and managed under three different surveillance scenarios: targeted trapping at high-risk locations (e.g. ports and firewood depots), routine health and safety inspections, and voluntary surveillance by land managers. 

The results show that early detection of the emerald ash borer is difficult because the larvae remain hidden inside trees for several years before symptoms appear. Official traps placed near ports and depots helped delay the spread in some cases, but trapping alone rarely led to eradication.

Routine tree inspections carried out for health and safety reasons proved to be important in the delay of EAB spread. Although they typically detect the beetle when trees are already in decline, these actions slowed local spread by prompting reporting and statutory response. 

Volunteer-based surveillance, in which land managers visually assessed trees for signs of EAB or deployed traps on their own land, appears to have great potential for pest detection. However, uptake of voluntary monitoring is heavily affected by land managers’ awareness, perceived efficacy of detection and management, and costs. When the model included financial support for traps, eradication became feasible in a small but meaningful fraction of the scenario simulations.

Overall, eradication of the emerald ash borer was rare under standard assumptions, occurring in fewer than 1% of simulations. This reinforces a well-established principle: pests with long cryptic phases and capacity for long-distance spread are extremely challenging to eliminate once established.

What this means for land managers and policy makers

Land managers are often the first line of defence. Regular inspections, accurate reporting and participation in surveillance schemes could substantially reduce the rate of emerald ash borer spread. Even when eradication is unlikely, slowing its spread buys time, protects neighbouring sites and supports coordinated control.

Our research shows that clear guidance, trusted reporting routes and financial help for trapping are key to sustaining long-term engagement. Additionally, policies that recognise the practical and economic pressures that land managers face are more likely to succeed.

Emerald ash borer, if it arrives, will be difficult to manage. But this research shows that collective action by informed and supported land managers can make a measurable difference to the future of ash in Great Britain.