Sarah Browning: Gall on trees looks worse than it is

Several different types of galls are common on Nebraska trees, caused by the feeding or egg-laying activities of insects or mites. Either the physical damage done by the insect or its salivary secretions as it feeds causes the plant to increase its production of plant hormones. These plant hormones cause abnormally increased plant growth in small, localized areas and result in the formation of a gall. Homeowners often become quite alarmed when they discover their tree is developing galls. They fear the tree is going to die unless something is...