Neuroterus numismalis

Silk button gall

Description

The species has two alternating generations. The gall of the spring sexual generation is a small (ca. 3 mm in diameter), unilocular leaf, in vein axils or at the leaf margin. This gall matures in May, the adults emerge in June. The gall of the autumn generation is a spangle gall mainly on the under side of the leaves. The entire surface of the gall is covered by bright silky hair, resembling a silk button (hence its English name). The gall most often found in larger groups covering most of the leaf surface. Regularly more abundant on late budburst trees. The asexual generation matures in autumn. Development continues while the gall overwinters in the leaf litter, and the adult emerges in April. The galls in high abundance may distort the leaves, otherwise the influence is negligible.

Symptom

Galls on leaves. The entire surface of the gall is covered by bright silky hair, resembling a silk button (hence its English name). The gall most often found in larger groups covering most of the leaf surface.

Tree Species: Oak

Part of a plant- attacked: Leaf / Needle

Pest significance: Less harmful

Pest Category: Insects

Invasive Species: No

Present in EU: Yes