Chirosia betuleti

Description

The knotting gall, is caused by the fly Chirosia betuleti (Ringdahl, 1935). The gall develops in the terminal shoots of ferns, such as broad buckler fern (Dryopteris dilatata), male fern (Dryopteris filix-mas), lady fern (Athyrium filix-femina), and ostrich fern (Matteuccia struthiopteris).