Interaction evaluation of glyphosate, glufosinate, chlorimuron and thifensulfuron combinations

The stacking of genes to provide resistance to several herbicides previously injurious to a crop provides new opportunities for control of a larger range of species and herbicide resistant weeds. Studies were conducted in the field in 2008 and 2009 and in the greenhouse from 2008 to 2010 to evaluate the combination of glyphosate and glufosinate and the sulfonylurea herbicides, chlorimuron and thifensulfuron on four weeds prevalent in Michigan cropping systems; common lambsquarters, velvetleaf, giant foxtail and Canada thistle. Antagonism was observed with combinations of glyphosate and glufosinate, glyphosate and chlorimuron and glufosinate and both sulfonylureas. Fluorescence measurements of leaves of the treated plants were taken in the greenhouse at 2, 4, 6, 8, 24, 48 and 72 hours after treatment to determine the time of herbicides injury to the plant photosynthetic system. Fluorescence parameters showed glufosinate acted within 2 hours after treatment and glyphosate within 24 hours after treatment. Absorption and translocation of 14C-glyphosate and 14C-chlorimuron was examined in the greenhouse to determine the basis for the observed interactions. The addition of chlorimuron increased absorption and translocation of 14C-glyphosate and the addition of glyphosate to 14C-chlorimuron also increased absorption and either decreased or had no effect on translocation out of the treated leaf.