With tree disease increasing in the UK, it is becoming more important than ever to be able to properly recognise the different types of the more common diseases plaguing our woodlands. By recognising the disease, and informing relevant forestry agencies and / or tree surgeons such as ourselves, we can help keep them under control.
Dutch Elm Disease
Perhaps the most well known of the diseases that can ravage our trees, Dutch Elm disease is passed on by elm bark beetles. This disease is so virulent and damaging that in just two outbreaks of the disease, around 25 million elm trees were lost.
The disease has declined in recent years but because it ravages the elm population so ‘successfully’ and no cure exists, it is important that new cases be reported. In this way, the disease can be tracked and hopefully headed off before it can cause any damage.
Dutch Elm Symptoms
- Yellow and wilting leaves in early summer
- Twigs can turn down and curl
- Dark streaks under the bark, cross sections can contain rings and or spots
This disease can infect more than just one tree species, making it a particularly dangerous disease for forestry. Otherwise perfectly healthy trees can be fatally struck down by Phytopthora Ramorum. Identified in the 90s, the disease affected oak trees first, passing to larch trees, chestnuts and the beech.
Something to keep in mind about this disease is that it doesn’t just affect trees because it can also infect plants such as the rhododendron too. First discovered in south west England, killing large numbers of larch, the disease has slowly spread to other parts of the UK.
Phytopthora Ramorum Symptoms
- Black seepage on the trunk, drying to a crust
- Discolouration under the seepage
- Lesions on the trunk
- Wilted and withered leaves, with blackened ends and needles
A major threat to the natural habitats of the United Kingdom, Ash dieback was identified in 2012. Infected trees will not recover although larger trees can live on for longer before finally succumbing to the disease. The infection is spread by spores which are dispersed by the wind and can cover a large area in a relatively short space of time.
Right now there are something in the region of 130,000 hectares of woodland at risk, and approximately 12 million trees outside of these woodlands. It’s easy to see why Chalara dieback is such a threat to the ash tree, and why it has to be closely tracked.
Chalara Dieback Symptoms
- Diamond shaped lesions on the trunk
- Black and dead leaves, resembling frost damage
- Brown leaf stalks and veins
- Dead tops on saplings
Acute Oak Decline
This disease has been around for the past 3 decades, affecting the native British oak. While it has been spotted in younger trees, it predominantly affects trees of at least 50 years. Thought to be bacterial in nature it is also thought that the buprestid beetle could also be at least partly to blame.
The majority of trees that are infected with Acute Oak Decline are dead within 5 years of the symptoms appearing. Thousands of oak trees have died so far but it seems that at least some oak trees are capable of recovery.
Acute Oak Decline Symptoms
- Black seepage on trunks
- Vertical splits in the bark
- Thinning canopy towards end of life
It is important that forestry is protected, not just because the trees themselves need to be preserved but because they also provide habitats for multitudes of species that otherwise would struggle to survive by themselves. If you think you have spotted something that matches one of the diseases here, don’t keep it to yourself.