The gall midge,Cystiphora schmidti, imported from Greece via Australia, readily attacks representative plants ofChondrilla junceaobtained from skeletonweed infestations throughout the United States. A strain ofAceria chondrillaefrom Greece (via Australia) attacked but did not form galls on the American strains of skeletonweed. The Vieste (Italy) strain ofAceriareproduced and formed varying amounts of gall tissue on all United States plants tested.