Application of a bacterial pathogen, Ralstonia solanacearum, with a wet-blade mower for biological control of tropical soda apple, Solanum viarum. (Special Issue: Bioherbicides.)

摘要

Tropical soda apple (Solanum viarum Dunal; TSA) is an invasive noxious weed in Florida and several southeastern U.S. states. To develop a bioherbicide agent that could be integrated with mowing, a recommended management practice for TSA, we screened several isolates of bacterial pathogens of Solanaceous plants and established that a Ralstonia solanacearum (=Pseudomonas solanacearum) (RS) isolate (10 Q, Race 1), originally from tomato, was capable of killing TSA without affecting tomato. RS is a xylem-invading, wilt-causing pathogen that when applied to cut main stems of TSA prevented regrowth and killed TSA plants under greenhouse conditions. To determine the effectiveness of this model bacterial bioherbicide agent under field conditions, a novel application method using a wet-blade mower was tested. Whereas wet-blade systems are used to deliver chemical herbicides and plant growth regulators to target weeds while mowing, none has been tested to deliver a biocontrol agent. We used the Burch Wet BladeTM mower system (BWB) and conducted the study in a pasture with 18% TSA coverage. RS cells suspended in sterile tap water at 1.4x109 CFU units/ml were used as inoculum. Treatments included a BWB-applied control (culture medium without RS), RS applied at 23 L/ha with BWB, and RS applied at 23 L/ha with BWB plus RS over-sprayed at 560 L/ha with a backpack sprayer. Both RS treatments reduced TSA regrowth compared to the control (P=0.0003). There was no difference between the wet-blade-applied RS treatment and the wet-blade+over-sprayed RS treatment. The wet-blade mower was an effective, practical means of application of the bacterial wilt pathogen to control TSA and it may have broader applicability to other types of wilt-causing pathogens.