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Title: Interaction of a bioherbicide and glyphosate for controlling hemp sesbania in glyphosate-resistant soybean

Author
item Boyette, Clyde
item Hoagland, Robert
item Weaver, Mark

Submitted to: Weed Biology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2007
Publication Date: 3/13/2008
Citation: Boyette, C.D., Hoagland, R.E., Weaver, M.A. 2008. Interaction of a bioherbicide and glyphosate for controlling hemp sesbania in glyphosate-resistant soybean. Weed Biology and Management. 8:18-24. doi:10.1111/j.1445-6664.2007.00269.x.

Interpretive Summary: The bioherbicidal fungus Colletotrichum truncatum was tested at different inoculum concentrations with different rates of the synthetic chemical herbicide glyphosate for control of the troublesome weed hemp sesbania in glyphosate-resistant soybeans. Hemp sesbania control and disease incidence were enhanced at the two lowest fungus and herbicide rates when fungal spores were applied after herbicide treatment. Application of the fungus in combination with, or prior to, glyphosate resulted in reduced disease incidence and weed control regardless of inoculum concentration. These results suggest the possibility to utilize herbicide and pathogen interactions to enhance hemp sesbania control with this fungus.

Technical Abstract: The bioherbicidal fungus Colletotrichum truncatum (Schwein.) Andrus & Moore was tested at different inoculum concentrations alone, and in combination with, prior to, or following treatment with different rates of glyphosate [N-(phosphonomethyl)glycine] (Roundup UltraTM) for control of hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill] in Roundup ReadyTM soybean plots. C. truncatum and glyphosate were applied in all pairwise combinations of 0.125 x 107, 0.25 x 107, 0.50 x 107, and 1.0 x 107 spores ml-1 and 0.15, 0.30, 0.60, and 1.2 kg ha-1, respectively. Weed control and disease incidence were enhanced at the two lowest fungus and herbicide rates when fungal spores were applied after glyphosate treatment. Application of the fungus in combination with or prior to glyphosate at 0.30 kg ha-1 resulted in reduced disease incidence and weed control regardless of inoculum concentration. At the highest glyphosate rates weeds were controlled by the herbicide alone. These results suggest that it may be possible to utilize additive or synergistic herbicide and pathogen interactions to enhance hemp sesbania control.