How tree health is protected in Scotland

Bark beetles are insects which bore into tree bark to lay their eggs. The larvae then feed on the inner bark of the tree.

In a healthy forest bark beetles are an important part of the ecosystem helping to decompose trees and providing food for other wildlife.

The two invasive conifer bark beetles we’re worried about

These species are not native to Scotland but can survive here and could cause widespread damage:

• Ips typographus, the eight-toothed spruce bark beetle
• Dendroctonus micans, the great spruce bark beetle

Another two invasive beetles, Ips cembrae and Ips sexdentatus, are not currently causing serious problems, but we are watching them carefully. 

Invasive bark beetles are a threat to scotland’s softwood trees.

1. Prevent

Reduce the risk by keeping your trees healthy

Prevention is better than a cure. Use standard good forest management strategies to make your forest healthier, more resilient, and more profitable. Then if invasive bark beetles do arrive, they are less likely to become established. 

Helpful strategies to reduce the risk of invasive bark beetle attack include regular monitoring and good forest hygiene, e.g. removing recently dead, infested, stressed, or damaged host trees. 

Be particularly vigilant after storms or other extreme weather

Bark beetles thrive in trees which are living, but stressed or damaged

Regularly identify, and, where possible, plan to remove them. 

Look out for damage caused by wind, snow, forest operations, animals, or recreation, as well as trees weakened by successive droughts, disease, or other environmental stressors. Freshly windblow trees are particularly vulnerable to infestation.

2. Monitor

Be alert for signs of invasive bark beetles

Report anything concerning to TreeAlert.

Invasive bark beetle larvae feed on the phloem and weaken trees by restricting the flow of nutrients.

As a result, infested trees can look obviously stressed with:

• bronzing foliage
• needle loss
• dead tops

You may also notice increased woodpecker activity (as woodpeckers feed on the larvae). 

If you investigate further, you might see beetles, larvae, or larval galleries under the bark. 

Resin tubes around entry holes on the bark are a characteristic symptom of D. micans. The impact and spread of D. micans can be reduced with biological control. 

Forest Research may contact you to arrange this following your Tree Alert report.

3. Adapt

Plant forests that are fit for the future

It’s more important than ever to plant the right tree in the right place for the right purpose.

If you are planning a new forest or restocking after felling, you can design a site that will be more resilient to bark beetles (and other threats) now and in the future.

• assess the site using tools like myForest (mapping, planning and sustainability), Ecological Site Classification (tree species choice) and ForestGALES (risk of wind damage) - sites at higher risk of drought or storm damage are more vulnerable
• choose trees which suit the site and are more ‘futureproof’. Forest Research have produced a shortlist of 14 conifers which are well suited to Scotland’s current and likely future climate
• diversify planting as much as feasible with no more than 65% of a single species. We don’t know what the future will hold so planting a mix of trees, including both conifers and broadleaf species, helps spread the risk
• to minimise the risk of bark beetle attack as your trees mature consider a Low Impact Silvicultural System (LISS) such as continuous cover forestry
• develop contingency plans for pest outbreaks