Threats to tree health
Both native and introduced trees in Wales are potentially susceptible to a wide range of pests and pathogens, as well as abiotic sources of damage such as extreme weather and pollution.
Trees can support populations of many insects and fungi without suffering serious damage. From time to time population explosions, unusual weather conditions or the introduction of a new pest can lead to trees being badly damaged or even killed. Outbreaks of pests and diseases which affect large numbers of trees can have significant effects on our landscapes, natural habitats and economy.
Occurrence of new pests and diseases
There has been an increase in the occurrence of new pests and diseases in recent years. This appears to be linked to the increase in global trade and travel and the associated movement of plants, wood products, wood packaging and other potentially infected or infested material.
Climate change may alter the area over which conditions are suitable for particular pests and diseases. For example, the pine processionary moth (Thaumetopoea pityocampa), a Mediterranean species, is thought to be moving northwards with climate change.
Extreme weather events may potentially change the behaviour of native and introduced pests and diseases in unpredictable ways. Climatic stresses such as drought may leave trees more vulnerable to attack.
Pests and diseases currently in Wales
In the last few years, the outbreaks of P. ramorum (Phytophthora ramorum), Chalara dieback of ash (Chalara fraxinea) and Acute oak decline have raised the profile of tree diseases in the UK and Wales.
The impacts of ramorum disease has forced the clearance of very large areas of larch, especially in the South Wales valleys.
Potential threats in the UK
Some pests and diseases already present or intercepted in other parts of the UK could pose a threat to trees in Wales if allowed to spread.
Plants, seeds and fruit from outside the UK
Plants, seeds, fruit, flowers or vegetables you find overseas should not be brought back to the UK as they can carry pests and diseases that would destroy UK plants, trees and crops.
How we all can protect our trees
There are steps everyone in Wales can take to help protect our trees:
- Be aware of the current and potential threats to trees
- Know how to identify pests and diseases and how to report them
- Take simple precautions when visiting the countryside to avoid spreading pests and diseases