Bur Oak March 2010 in Billings
Oak Galls are formed by infestation of gall makers. There are hundreds of different types of gall makers including gall wasps, midges, aphids and mites. The tree is stimulated by the presence of these organisms to produce abnormal plant cells that serve as protection for the pests. The inner wall of the galls provide a source of protein for the young larvae. The appearance of galls varies in the size, colour, shape and hairiness. The variation depends on the type of gall maker infecting the tree. The galls are obvious growths on tree branches detracting from the overall appearance of the tree.
