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Andricus pictus

Gall wasp Andricus pictus

Description

Andricus pictus and Andricus dentimitratus are two similar (according galls shape) European gall wasps (Hymenoptera: Cynipidae) that form galls on various oak species (Quercus spp.). Andricus pictus specifically induces galls on Mediterranean oak species such as Quercus faginea, Q. pyrenaica, Q. lusitanica, and occasionally Q. robur. This species is closely associated with Mediterranean marcescent oaks and is widely distributed in southwestern Europe, particularly in the Iberian Peninsula. Studies indicate that A. pictus and A. dentimitratus have complementary distributions within the Iberian Peninsula, separated by the Ebro Valley. A. dentimitratus is primarily found northeast of the valley, while A. pictus is distributed southwest of it. This distinct pattern may be influenced by climatic differences or the specific distribution of their respective host oak species.

The wasp induces galls that form on acorns or occasionally on buds. Fresh galls are bright red, sticky, and shaped like a low cone with slender protrusions at the base. As they age, the galls dry out, harden, and turn brown. While these galls do not significantly harm the tree's health, heavy infestations may reduce acorn production and affect the aesthetic appearance of the host tree.

Symptom

Galls are conical with slender extensions at the base, initially bright red and sticky, later turning brown and dry. They occur on acorns or buds, often distorting the affected parts.

Tree Species: Oak

Part of a plant- attacked: Fruit / Seed

Pest significance: Less harmful

Pest Category: Insects

Invasive Species: No

Present in EU: Yes