I found a nice article on Galls on various species of trees which are caused by insects. The article is titled “Galls On Trees” and was written by the Missouri Botanical Garden. The article discusses Galls and how to manage them. There are many photos of different galls on different species to look at. My neighbor has Nipple Gall on her Hackberry landscape trees for years. She refuses to spray for them and they have finally invaded my yard. I now have them on several different species, mostly Chokecherries. None on the Bonsai trees yet. I have treated my landscape trees with Bayer Advanced and I will  have to see what happens next spring. I have added the article to the Diseases/Insects page under Bonsai Basics.

Photo Courtesy of Missouri Botanical Garden

Photo Courtesy of Missouri Botanical Garden

Photo Courtesy of Missouri Botanical Garden