Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Galls are abnormal plant tissue growths and can be caused by a variety of organisms, and most of the galls we notice are only cosmetically damaging. But Bacterial crown gall affects a wide variety of orchard fruits and is caused by the pathogen Agrobacterium tumefaciens – tumefaciens meaning causing tumors. This fungus is capable of causing harmful growths on more plant species than any other pathogen. Only monocots are immune. It causes obstructive galls to develop on the plant, blocking nutrient and water distribution. A wound or injury to the plant allows the fungus to invade it – injuries that can come from pruning wounds, soil insects that feed on plant roots, machines being used in the field, or even freezing temperatures. The bacterium can live in the soil for many years and prevents growers from being able to use that field productively.