The Forestry Commission’s visual guide to tree damage
Grey squirrel and deer damage to trees: Visual guide
How to spot tree damage by deer and grey squirrels
Grey squirrels and deer can damage young and mature trees, by eating young shoots and stripping bark which can result in tree loss. Missing bark can make the tree more susceptible to infections, and these wounds can restrict the future use of the tree and any timber produced, or can even kill the tree. Knowing how to spot the early signs of grey squirrel and deer damage allows you to put effective mammal management in place before significant damage is done.
Grey squirrel damage to trees – what to look out for
Grey squirrels are a non-native invasive species notorious for stripping the bark from a tree’s main stem and branches. The damage they cause prevents the flow of water and food around the tree, putting significant stress on it – weakening and, if severe enough, eventually killing the tree. It’s important to regularly inspect woodland and individual trees for signs of damage – which typically occurs in spring – from February onwards.
Grey squirrels favour young broadleaf trees that are between 10 to 40 years old. Oak, beech and sycamore are particularly vulnerable to squirrel damage, while some broadleaf species such as lime, horse chestnut and wild cherry are less favoured by grey squirrels. The cost of bark stripping caused by grey squirrels in England and Wales is estimated to be at least £37 million-a-year.
Managing grey squirrels in your woodland
Grey squirrel management measures to protect vulnerable trees in your woodland are carried out in the spring. Adopting a mixture of management measures is generally most effective, and these include:
Trapping – Placing traps specifically licensed for grey squirrels helps ensure you are complying with the law. Guidance on the number and location of traps must be followed.
Shooting – This can be an effective way to reduce their numbers, but is most effective when combined with trapping.
Fertility control – An oral immunocontraceptive is being developed to offer an alternative or complementary non-lethal and humane management method.
Deer damage to trees – what to look out for
There are six species of deer that inhabit UK woodlands, two of which are native – the red deer and the roe deer – while fallow, muntjac, sika and Chinese water deer make up the other non-native species. The population of all six species have drastically increased, growing from around 450,000 to approximately two million in the past 50 years.
Large deer populations prevent forests from naturally regenerating, as they kill or suppress seedlings. Damage to bark can cause structural weakness and allow diseases to enter, and woodland diversity can also be negatively impacted as deer can damage habitats for other woodland species in the process. Deer browsing damage can reduce timber crop values by up to 30-50%, costing some landowners as much as £1 million annually.
Managing deer in your woodland
It’s often best to adopt a mixture of management measures to protect your woodland. Deer management measures include:
Culling – Culling or lethal control needs to be well planned and managed to be effective in the long-term. Keeping records and having proper training is essential, but the venison produced can also help you to offset the cost of deer management.
Fencing – Well erected and maintained deer fencing can provide adequate tree protection especially for young trees – to help them establish. You need to check fencing regularly and keep gates shut, and this method should also be used in conjunction with a form of lethal control.
Deterrents – If fencing is not an option for you, the application of lanolin-based spray-on deer detergents can be considered to manage low deer populations.
Tree shelters – Protecting individual trees with plastic or more substantial timber guards can help to shield young trees from deer. Ensure tree shelters are appropriate to the deer species present, and be aware that deer can still damage sheltered trees.
Click here to read the full Forestry Commission’s guide.