Disclosure is provided for methods of preventing, removing or inhibiting microbial biofilm formation or microbial infection in a plant or plant part thereof, including applying thereto a treatment effective amount of an active compound as described herein, or an agriculturally acceptable salt thereof. Methods of enhancing a microbicide (e.g., including a copper, antibiotic, bacteriophage, etc.) and/or plant defense activator are also provided, including applying an active compound as described herein. Compositions comprising an active compound as described herein in an agriculturally acceptable carrier are also provided, and in some embodiments the compositions further include a microbicide (e.g., including copper, antibiotic, bacteriophage, etc.) and/or plant defense activator.