Synergizing Weed Biocontrol Agents with Chemical Herbicides

Abstract

Enhanced weed control can occur when chemical herbicides are applied in combination with microbial agents. Synergy between chemicals and biologicals was first observed with fungal bioherbicides. Use of a herbicide with a fungal-bioherbicide does not appear to widen the weed spectrum of the bioherbicide but does increase the efficacy. In some cases the synergy may result from a suppression of phytoalexin synthesis by the chemical herbicide. Use of synthetic herbicides to synergize mycoherbicides will in some cases reduce herbicide use rate and improve mycoherbicide efficacy. We report here that synergy occurs between chemical herbicides and bacterial agents. We have discovered that bacteria which cause little or no injury to weeds when applied alone can enhance the stability of low levels of chemical herbicides to control a broad spectrum of weeds. We term this synergistic combination the X-tend system. In the first year of X-tend field trials, the level of weed control required for commercialization was not obtained consistently across geographic locations. Consistency will need to be improved through selection of more robust microbial strains and/or improvements in formulations