Glyphosate continues to be one of the most widely used herbicides in soybean production systems despite resistance in several key species. Most growers still utilize glyphosate as a base herbicide to control 95% or more of the weed species found in their fields, especially grass species. As we have needed to utilize other herbicides to control glyphosate-resistant species, there have been complaints of lack of control where combinations of auxin herbicides and glyphosate with or without adjuvants have been observed. In addition, there have been concerns about efficacy of new glyphosate formulations compared to control observed in previous years with older formulations. We plan to test these different concerns around glyphosate through greenhouse and field studies to determine if differences in control or antagonism are present.

Numerous concerns have been raised about activity of various new glyphosate formulations for weed control, and specifically grass weeds when glyphosate is applied with auxin herbicides or adjuvants. Therefore field and greenhouse studies will be conducted to determine:
1) If weed control is affected by formulation of new glyphosate products on the market.
2) If grass weed control is affected by tank-mixes of glyphosate with Auxin herbicides.
3) If grass weed control is affected by adjuvants in combination with glyphosate.
4) Summarize and extend results and findings and report to Association and stakeholders.

Detailed material on glyphosate formulations and potential antagonism issues should be developed and made available through Extension presentations, Extension fact sheets, popular press articles, Extension videos, and other appropriate venues so growers have a greater understanding of what issues are currently here so effective control decisions can be made. In addition, this will be part of a graduate student project and an end product will be a well-trained student with a strong understanding of herbicide interactions and control issues in North Carolina.

Identifying concerns and rapidly determining if there are issues is a primary concern for the Weed Science program at NC State. If there are antagonistic combinations, or reduced control with various formulations, we need to be able to advise growers on alternative solutions and ways to avoid issues in their fields.