Submitted to: Natural Areas Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2007
Publication Date: July 1, 2007
Citation: Weaver, M.A., Lyn, M.E. 2007. Compatability of a Biological Control Agent with Herbicides for Control of Invasive Plant Species. Natural Areas Journal 26:264-268. Interpretive Summary: Control of kudzu typically requires several years of herbicide application, which is expensive and not advised near certain sensitive sites. Thus, it is common practice to use a combination of strategies for controlling this invasive weed. The fungus, Myrothecium verrucaria (MV), offers great potential as a bioherbicide for control of kudzu and other invasive vines. This is part of research directed towards an integrated management system for controlling kudzu using MV with herbicides. In this study the compatibility of MV with herbicides commonly used in forestry, rangeland and natural areas was evaluated by evaluating the exposure time that could be tolerated by MV spores in tank-mix suspensions of three herbicides at three concentrations, with appropriate spray adjuvants. All tested concentrations (up to the maximum labeled rate) of aminopyralid and metsulfuron were well-tolerated for up to 48 hours and did not inhibit growth of MV in agar culture. Fluoxypyr, in contrast caused a gradual loss of viability over time, especially at higher concentrations, and reduced the growth rate of MV in agar culture. These studies provide insight in selecting appropriate herbicides for mixing with this novel biocontrol fungus in an integrated control strategy for kudzu.
Technical Abstract: Kudzu, Pueraria montana var lobata, is an exotic invasive weed that is difficult to control with available products and management practices. The fungal pathogen, Myrothecium verrucaria, is being developed as a bioherbicide for kudzu and other invasive vines. This biological control agent might be applied with conventional herbicides to improve the efficacy or spectrum of weed control. The survival of M. verrucaria was measured over time in simulated tank-mixes of of commercial formulations of the herbicides amniopyralid (Milestone*), metsulfuron (Escort XP) and fluoxypyr (Vista). The fungus was also grown in vitro in the presence of these herbicides to evaluate any growth inhibition caused by these products. M. verrucaria was highly tolerant to all tested concentrations of amniopyralid and metsulfuron for up to two days in simulated tank-mixes, while mixtures with fluoxypyr resulted in a gradual loss of spore viability. The fungus grew on media supplemented with amniopyralid and metsulfuron with only small effects on the growth rate, but fluoxypyr caused growth inhibition. These studies provide insight for developing effective, integrated control stratagies for kudzu.