HERBICIDE INJURY DETECTION USING BIOCHEMICAL METHODS

Herbicides are intended to control weeds but sometimes erroneous applications can cause injury to desirable plant species. Recent biochemical diagnostic tools are being made available to turf managers and custom applicators to identify various herbicide injuries. Glyphosate (Roundup^®) acts on the enzyme 5-enol pyruvyl shikimate 3-phosphate synthase (EPSPS) in the biochemical pathway to disrupt the synthesis of three aromatic amino acids, resulting in an accumulation of a particular chemical in plants called shikimate. Experiments were conducted in the field and laboratory on creeping bentgrass to detect herbicide injury due to various glyphosate based-formulations. Two dry herbicide formulations (Roundup ProDry^® and QuikPRO^® powered by Roundup^®) were included in the experiments. All glyphosate-based herbicide treatments were applied on a kg ae (acid equivalent) glyphosate per hectare basis and were compared to glufosinate (Finale^® 2SC) treatment applied at 1.7 kg ae ha^-1. Glyphosate-based herbicides were applied at three different rates (5, 5.88 and 6.8 kg ae ha^-1). Plant tissues were analyzed for the presence of shikimic acid at 48 and 72 h after the application of herbicides and the amount of shikimate was quantified. Within 48 h after treatment Roundup ProDry resulted in a higher amount of shikimate in the plant tissues compared to the untreated check and the QuikPRO powered by Roundup treatments. After 72 h there was no difference in the amount of shikimate in the plant tissues between the different glyphosate formulations. Based on the amount of shikimate accumulation in plant tissues it was possible to identify the herbicide injury on turfgrasses.