O-68

Interactions of tank mixed combinations of glyphosate, glufosinate, chlorimuron and thifensulfuron.

Rachel Bethke, Donald Penner, Christy Sprague, Wesley Everman
Michigan State University, East Lansing, MI, USA

The introduction of double and triple stacked herbicide resistant traits corn and soybeans allows for combination of these herbicides in the tank. Tank mixing herbicides could allow for control of resistant weeds but past studies have shown antagonism between herbicide combinations. Two years of field and greenhouse studies were conducted on the annual weeds velvetleaf, common lambsquarters and giant foxtail and the perennial weed Canada thistle to determine the efficacy of all combinations of glyphosate, glufosinate, chlorimuron and thifensulfuron at labeled and lower rates. Data for visual control, height and weight reduction, senescence, leaf fluorescence, shikimic acid and glutamine synthetase assays, and 14C-labeled herbicide translocation and absorption studies, support the hypothesis that combining slow acting and fasting herbicides may result in interactions. Both antagonistic and synergistic interactions were observed depending on herbicide applied and weed species.