Spined or Horned Galls on Oaks in Florida Induced by Gall Wasps, Callirhytis quercusclaviger (Ashmead) and Callirhytis cornigera (Osten Sacken)

Callirhytis quercusclaviger (Ashmead) causes the “spine-bearing potato gall” on laurel oak, Quercus laurifolia Michx., in Florida (Ashmead 188i). The horned oak gall, caused by Callirhytis cornigera (Osten Sacken), occurs on water oak, Quercus nigra L., as well as several other Quercus spp. (Drooz 1985; Osten Saken 1862). Generally, individual trees or small groups of trees become slightly to moderately infested by these Callirhytis spp. Widespread infestations are not common (Kinsey 1935). However, severe gall wasp infestations have been observed recently in several Florida counties. Extremely high numbers of twig galls of C. quercusclaviger have occurred on thousands of laurel oaks in several locations. These infestations have affected young to mature trees in woodlands and residential areas. The overabundance of twig galls has resulted in notable levels of branch dieback, crown thinning, and tree mortality.