California Gallfly
50 host plants
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Round, apple-shaped galls up to an inch across appear on Oregon white oak twigs and branches in late spring and summer, caused by the California gallfly wasp. You will notice these conspicuous growths clustered on branch tips and small twigs. Each gall houses developing wasp larvae inside a hard, woody structure. The galls persist on branches long after the wasps emerge.
This pest is cosmetic on established Oregon white oaks and does not threaten tree health. Prune out heavily galled branches during dormant season if the appearance concerns you. The galls support a complex community of parasitic wasps that help regulate gallfly populations naturally. No chemical control is necessary or recommended.
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Host Plants
50
Host Plants (50)
Quercus acutissima Sawtooth Oak Quercus agrifolia Coast Live Oak Quercus alba (Eastern) White Oak Quercus arizonica Arizona Oak, Arizona White Oak Quercus berberidifolia California Scrub Oak, Scrub Oak, Inland Scrub Oak Quercus bicolor Swamp White Oak Quercus bimundorum Two Worlds Oak, Bimundors Oak Quercus castaneifolia Chestnut-leaved Oak, Chestnutleaf Oak, Persian Oak Quercus cerris Turkey Oak Quercus chrysolepis Canyon Live Oak Quercus coccinea Scarlet Oak Quercus douglasii Blue Oak, California Blue Oak Quercus durata Leather Oak Quercus emoryi Emory Oak, Black Oak, Blackjack Oak Quercus engelmannii Engelmann Oak, Mesa Oak Quercus frainetto Hungarian Oak, Italian Oak Quercus gambelii Gambel Oak, Rocky Mountain White Oak Quercus garryana Oregon White Oak Quercus garryana var. breweri Brewer's Oak Quercus glandulifera Konara Oak Quercus glauca Japanese Blue Oak, Ring-cupped Oak Quercus hypoleucoides Silverleaf Oak, Whiteleaf Oak Quercus ilex Holly, Oak, Holm Oak Quercus ilicifolia Bear Oak Quercus imbricaria Shingle Oak Quercus kelloggii California Black Oak Quercus leana Lea's Oak Quercus lobata Valley Oak, Roble Oak, California White Oak Quercus macrocarpa Bur Oak, Mossycup Oak Quercus marilandica Blackjack Oak, Jack Oak Quercus mongolica Mongolian Oak Quercus montana Mountain Chestnut, Oak, Chestnut, Oak, Rock Chestnust Oak Quercus muehlenbergii Chinkapin Oak, Chinquapin Oak, Yellow Chestnut, Oak Quercus myrsinifolia Chinese Evergreen Oak, Bamboo-leaf Oak Quercus nigra Water Oak, Possum Oak Quercus palustris Pin Oak, Swamp Spanish Oak Quercus petraea Sessile Oak, Durmast Oak, Irish Oak Quercus phellos Willow, Oak Quercus prinoides Dwarf Chinquapin Oak, Dwarf Chestnut, Oak, Scrub Chestnut, Oak Quercus robur English Oak Quercus rubra Northern Red Oak Quercus sadleriana Sadler Oak, Deer Oak Quercus stellata Post Oak Quercus suber Cork Oak Quercus turbinella Scrub Live Oak Quercus undulata Wavyleaved Oak Quercus vaccinifolia Huckleberry, Oak Quercus velutina Black Oak Quercus virginiana Southern Live Oak, Live Oak Quercus wislizeni Interior Live Oak, Chapparal Oak