July 6, 2021

Most Common Tree Diseases & Pests in the UK: Identification and Endangered Trees

Introduced, pest related, or viral diseases are damaging to native trees here in the UK, some of which have been standing for hundreds of years.

Good biosecurity practice is becoming a growing priority and the UK government have labelled the “damage to our trees, woods and forests from insect pests and organisms” as “significant.” More importantly, this interest is now shared by both the public and corporations alike, who are actively taking responsibility for nurturing the environment though initiatives like planting native trees.

Since the 2000’s, the demand for rare and exotic hardwoods, the increasing use of timbers in transport, and an interest in exotic or different plants has resulted in a harmful growth of imported pests and bacteria from abroad. Many developments, including natural pests and disease, have created an urgency to better understand our trees and the challenges they face.

Trees are under pressure all the time from a variety of diseases and pests, which can have dire consequences on their health. From leaf damage to wilting, these can be identified by common symptoms. Many businesses want trees to thrive rather than simply survive.

Which trees are most at-risk?

We’ve analysed data from the IUCN (International Union for Conservation of Nature and Natural Resources) about some of the most at-risk trees in the UK, either from pest or landscape changes.

Here’s what we discovered.

Critically endangered trees

The most endangered trees include:

Catacol Whitebeam
Arran Service Tree
Cheddar Whitebeam
Ship Rock Whitebeam
Green’s Whitebeam
Sorbus Spectans (A type of Whitebeam)

Another noticeable tree classified as ‘vulnerable’ is the horse chestnut, which is nostalgic for many living in the British countryside. Known for bearing conkers, these trees have been celebrated by children and are associated with autumn.

Common pests in the UK that affect native trees

While there are numerous blights that affect our native trees, the Woodland Trust has identified some major ones that negatively affect, or could majorly impact, our native woodlands.

Asian and Citrus Longhorn Beetles

At risk of being imported on wooden crates, and within infected plants such as bonsai trees, especially from China, this beetle is at high risk on damaging a wide range of broadleaf trees, including Alder, Birch and Whitebeam.

Bronze Birch Borer

The bronze birch borer are strong fliers, so they can spread quickly, and this poses a great risk to European and UK birch trees. To prevent an infestation, which could be detrimental to UK trees, imports on birch trees from the US or Canada is strictly prohibited.

Eight-Toothed Spruce Bark Beetle

Causing dieback of large parts of spruce trees as well as carrying a pathogenic fungus, this beetle was last found in the UK in 2018 after being accidentally imported. There is large concern for the impact it could have on our rare and protected Scottish pine forests. As you can see in the above image, the damage it can do is gargantuan.

Elm Zig-Zag Sawfly

Damaging Elm populations in the Southeast and East Midlands, the sawfly reached the UK in 2017. The larvae can seriously damage leaves, making the tree highly susceptible to further harm and any potential droughts.

Oak Lace Bug

While we have some native species of lace bug, none feed on oak as damagingly as this non-native species. While we do not have them in the UK currently, the risk is high, and can spread locally, affecting the process of photosynthesis for many populations of local trees.

Oak Processionary Moth

This moth causes damage to humans as well as trees. The irritating spines on the caterpillar cause rashes and itching in humans, making this pest dangerous to remove by hand.

Accidentally imported in 2006, it was initially confined to Greater London, but has since spread and was re-imported in 2019. This moth strips trees of their leaves and nests on oaks, making it hard for the oak to shed.

Red-Necked Longhorn Beetle

As the beetle lives in the trunk, there is no sign of an infestation until it is too late. Typically, this will affect trees like cherry trees. The beetles burrow and hide in the trunks in colder weather, only emerging as the temperature warms.

Diseases that are affecting UK native trees

To date, 60 million trees have died due to Dutch Elm disease, and we have six epidemic level pests and diseases in the UK. As our climate changes, disease becomes more prevalent and the warmer and damper weather accelerates this growth of bacteria.

There are some incredibly dangerous diseases and disorders out there, which include the following:

Ash Dieback

Predicted to affect 80% of Ash trees fatally, Ash dieback has the potential to kill, damage or harm numerous European species of ash. It doesn’t affect the native hosts where it originated in Japan, but for over 30 years has devastated European trees.

A toll that has cost taxpayers up to £15 billion to assist in the fight against ash dieback, it’s one of the biggest threats to native trees in the UK today.

Acute Oak Decline

Oak decline are phenomena that occur throughout history. The current one has been observed for 20 years or so, and older trees seem to be more affected, dying within five years. This type of decline is, typically, a response to environmental stress, although other factors can contribute.

Tree Diseases, Pests and the Law

Since Brexit, there is now different ‘plant passports’ that are required to import trees, plants, soil matter and more, into England, Scotland and Wales. To bring certain high risk plants and plant products into Great Britain you must now have a Phytosanitary Certificate (PC).

For moving plants around Great Britain, specifically in commercial settings, you will need a UK Plant Passport. This details information about the plant, it’s origin and more.

The UK Law on imported plants is strict, as we are easily able to control what pests, diseases and alien species are brought in with strict restrictions

The UK Law on imported plants is strict, as we are easily able to control what pests, diseases and alien species are brought in with strict restrictions.

Prevention of Tree Diseases and Pests

As well as issuing strict regulations on plant passports and sourcing trees, there are other measures that can be taken to prevent the spread.

Grounds Care Group complies with all biosecurity regulations, and our tree surgeons are kept up to date on any legal changes, especially post Brexit.

Why can tree surgery help you with pests and disease?

Tree surgeons and arborists are adept at spotting pests sooner than the untrained eye. Regular visits from tree surgeons can ensure the longevity of your trees.

At Grounds Care Group, we’re able to offer specialist tree surveys which can assist in identifying pests and disease earlier, including the symptoms that your trees might be under attack.