It is most often confused with insect galls but resembles the rust galls described on pine and a few fungal galls. Abnormal growths on plants, called burls, can resemble crown galls. The bark of the host usually remains on the burls but is not present on crown galls.
Crown gall is a disease caused by a bacterial patho-gen, Agrobacterium tumefaciens .
The bacterium en-ters the plant through a wound, and the plant forms a gall. Actually, crown gall is an odd plant disease. The bacteria cause uncontrolled cell division in the host plant, resulting in gall formation. Genetic coding from the bacterium becomes incorporated into the host s coding. As you can imagine, this system has been studied and used extensively in research on genetic manipulation.