Interaction of the bioherbicide Myrothecium verrucarria and glyphosate for kudzu control

Authors: Boyette, Clyde; Hoagland, Robert; Weaver, Mark; Stetina, Kenneth - Ken

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2014
Publication Date: 12/26/2014
Publication URL: https://handle.nal.usda.gov/10113/60824
Citation: Boyette, C.D., Hoagland, R.E., Weaver, M.A., Stetina, K.C. 2014. Interaction of the bioherbicide Myrothecium verrucarria and glyphosate for kudzu control. American Journal of Plant Sciences. 5:3943-3956.

Interpretive Summary: We have previously reported that formulations (spore or mycelia) of the fungal bioherbicide Myrothecium verrucaria (MV), exhibit bioherbicidal activity against kudzu and several other weeds, and that the herbicide glyphosate can act additively or synergistically with MV against some weeds. Glyphosate does not effectively control kudzu even applied above recommended rates. Recommended and sub-lethal concentrations of a mixture of MV spores or mycelia with a commercial formulation of glyphosate caused additive and/or synergistic effects on control of kudzu under greenhouse and field conditions. These results suggest that it may be possible to use combinations of glyphosate to improve bioherbicidal control potential and reduce herbicide and inoculum requirements of MV spores or mycelium for controlling kudzu. Furthermore these findings provide the basis for further characterization of MV and glyphosate interactions on weeds.

Technical Abstract: Spore and mycelial formulations of the bioherbicidal fungus Myrothecium verrucaria (MV) were tested alone and in combination with glyphosate for control of kudzu (Pueraria lobata) under greenhouse and field conditions in naturally-infested sites at Lexington and Eden, MS. Control of kudzu increased as the concentration of spores or mycelia increased. Glyphosate alone provided 10, 35, 50 and 60% control in field experiments at 0.25, 0.50, 0.75 and 1.0x, respectively and MV alone spores provided 15, 50, 65 and 85% control at 0.25, 0.50, 0.75 and 1.0x, respectively. However, when MV spores were combined with glyphosate, significantly higher control occurred than that caused by either component alone. Similar levels of control were observed for MV mycelial formulations applied alone or with glyphosate at equivalent concentrations of the fungus. Disease kinetics were more rapid and severe at all fungal spore or mycelial formulations and herbicide rates when these propagules were applied in combination with glyphosate. In field tests, 24 h after application, only 20% of kudzu plants were severely damaged by MV alone (0.25x), whereas 80% were severely diseased when MV spores and glyphosate were mixed and applied at 0.25x rates each. A similar trend occurred with the MV mycelial formulation applied at these rates. Synergist interactions on kudzu control were observed, especially when lower levels of MV (spores or mycelia) and glyphosate were combined and applied to kudzu in the greenhouse or in the field. These results suggest that it may be possible to incorporate glyphosate to improve the bioherbicidal control potential and reduce herbicide and inoculum requirements of M. verrucaria spores or mycelium for controlling kudzu.