Burnettweldia washingtonensis

The galls of Burnettweldia washingtonensis are distinguished by their detachable, spherical form with a short stem or neck, gray to beige fuzzy exterior, and 8–10 mm diameter. The interior is chocolate brown with a central larval chamber. Older galls may develop pitted surfaces. These galls are sometimes mistaken for those of Besbicus conspicuus, which induces similar stem galls on oaks.

Associated with white oaks (Quercus sect. Quercus) in coastal and near-coastal environments of the Pacific Northwest. The galls form on stems rather than leaves or buds.

Pacific coast of North America, from British Columbia south through Washington and Oregon to California.

• Quercus sect. Quercus - hostwhite oaks; stem gall inducer

Larval development occurs within the central chamber of the stem gall. The wasp emerges from the mature gall after completing development. Specific details of voltinism and overwintering strategy are not documented.

As a gall inducer, this species modifies host plant tissue to create protected larval chambers. The galls serve as microhabitats for a community of parasitoid wasps and inquilines. The European parasitoid Bootanomyia dorsalis has been reared from these galls on the Pacific coast, representing an introduced parasitoid association.

The species has contributed to research on oak gall wasp diversity and parasitoid community ecology. Its galls are readily identifiable and have been used in citizen science monitoring through platforms such as iNaturalist and Gallformers.org. The species was included in a 2024 NSF-funded study examining gall wasp-parasitoid coevolution across North America.

• Besbicus conspicuusInduces morphologically similar stem galls on oaks; galls are sometimes mistaken for those of B. washingtonensis in the field.

• gall wasp
• cynipid
• oak gall
• stem gall
• Pacific coast
• white oak

• BugGuide
• Wikipedia
• iNaturalist taxon
• NCBI Taxonomy
• Discovery of wasp species previously unknown in the U.S.