Transgenic Research released a review article authored by Monoj Sutradhar and Nirmal Mandal containing the reasons and preventive methods for the overgrowth of Agrobacterium tumefaciens during plant transformation.

Agrobacterium tumefaciens-mediated plant transformation has become routine work across the world to study gene function and the production of genetically modified plants. However, several issues hamper the transformation process in a profound way, both directly and indirectly. One of the major concerns is the overgrowth of Agrobacterium, which occasionally appears after the co-cultivation phase of the explant. This phenomenon is reported in several species and seems to spoil the whole transformation process. 

Reasons and riddance of Agrobacterium tumefaciens overgrowth in plant transformation | SpringerLink