Taphrina betulina

Witches’ broom

Description

Witches’ brooms on birch are the result of a persistant growth disturbance caused by Taphrina betulina. Stimulated by specific chemicals produced by the fungus, large numbers od the dormant buds flush, eventually forming densely branched, sphaerical bushes. The twigs infected by the fungus have onion-shaped swellings at the base of their side shoots. Asci of the fungus occur in early summer on the underside of the leaves. Hyaline spores begin to germinate even while they are still in the ascus. As the fungus overwinters in the buds and bark, birch brooms can live for many years. No economic significance is attached to witches’ broom on birch, although branches distal to them occasionally die.

Symptom

Stimulated by specific chemicals produced by the fungus, large numbers od the dormant buds flush, eventually forming densely branched, sphaerical bushes. The twigs infected by the fungus have onion-shaped swellings at the base of their side shoots.

Tree Species: Birch

Part of a plant- attacked: Branch

Pest significance: Harmful

Pest Category: Fungi

Invasive Species: No

Present in EU: Yes

Seasonal frequency of occurrence