Tree Surgery

Pests and diseases

Oak Die Back

Cause: Abiotic and biotic factors.

Early Symptoms: Leaves are smaller than usual over all or part of the crown. Leaves are sparser than normal and can be pale green or yellow.

Later Symptoms: Scattered dead twigs and branches throughout the crown

Final symptoms: Remaining foliage is pale or yellow with most of the branches and limbs having died back. Some trees that start to grow back with thin healthy shoots, known as epicormic growth, leave a large amount of dead wood above the healthy foliage this is known as Stag-Headed.

Confirmation: This disease the roots will be alive on the most severe die back. Other indications to look out for are patches of dead bark, dark tarry spots, removal of the bark to reveal a network of grooves approx 3-4mm wide on the outer wood or inner bark and the presence of the Buprestid beetle larvae. These are flattened, whitish translucent grub that are legless with a brown head.

Hosts: Quercus Robur and some hybrids from Quercus Robur through to Quercus Petraea.

Control: None.

Oak Leaf Phylloxera

(Fairly common in southern England)

Cause: Phylloxera insect.

Symptoms: Extensive browning of leaves in August. This may be on one or two bows only, rather than the whole tree. During late June to early July, small yellow dots approx 2mm in diameter will appear on the upper side of the older leaves. The spots increase in size and spread as the season progresses.

Host: Quercus Robur.

Control: Not normally considered.

Oak Slugworm

Cause: Oak Slug Sawfly (Caliroa Annulipes) insect.

Symptoms: Brown patches appear on the leaves in May and July and worsen in August. Removal of the lower epidermis, leaving a network of veins.

Confirmation: The brown patches appear translucent when held up to the light. Check for the moulted skin of the larvae to the leaf, with their front legs splayed out. Look for feeding, slug-like larvae that are yellowish green with dark heads, approx 10mm long and usually found in May, June or August.

Hosts: Quercus, Prunus, Fagus, Cratagus, Betula but most frequently on Tilia.

Control: Only on smaller trees where the infected leaves can be hand picked and destroyed.

Pine Shoot Beetle

Tomicus Piniperda (Common and widespread in the UK)

Damage Type: Localised destruction of main stem cambium.

Symptoms: The tree dies.

Confirmation: From June onwards, insect emergence holes about 1.5mm will apear in the thicker bark of the dead or dying trees (Shot Holes). From around March on live trees, the entry holes are often indicated by resin tubes on the trunk. If you remove a section of this bark, the beetle galleries are revealed in the cambium. Shoots on nearby infected trees will become brown later on in the year.

Hosts: Pinus. More susceptible are Pinus Sylvestris.

Control: Remove blown trees and cut logs as soon as possible from the vicinity as these can be potential breeding areas.

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