Grey squirrels damage trees by gnawing at the stem to get to the sweet, sap filled layers (phloem tissue) just beneath the bark. This tissue is responsible for the movement of sugars around the plant (known as translocation). If this gnawing extends around the stem so the tree is ‘ringed’ i.e. a complete circle of bark and underlying tissue is removed, then the movement of sugars around the plant will come to a halt and the tree will die. Removal of any bark and associated tissue will check or restrict the growth of trees.
This bark stripping occurs between late April and the end of July. Very young trees or saplings (stem diameter less than 5 cm) are generally not attacked as they cannot support the weight of a squirrel, the main stem of older trees (40 years+) are usually safe as the bark is too thick for the squirrels to strip.
The most vulnerable trees are sycamore, beech, oak, sweet chestnut, pine, larch and Norway spruce, aged between 10 and 40 years old; though almost any broadleaved species of tree can be attacked. Bark stripping is a problem in woodland where the squirrel numbers are greater than 5 squirrels per hectare. The risk of damage may be greatest where there are vulnerable trees next to mature woodland that produces a good seed crop, which in turn supports a high density of squirrels.
Some of the damaged trees will die, some will succumb to fungal infection. Where the fungus enters, the wood will become stained and may rot. In many cases, the stems will be deformed which reduces the value of the timber. If branches in the canopy are attacked, dieback may result and again the quality and quantity of timber produced is affected.
Please contact us if you are suffering tree damge by Grey Squirrels