Pyroxasulfone

Post resistance has taken most of the traditional cleanup options off the table in Southeastern ryegrass. That makes pyroxasulfone the best soil-applied tool we have for stopping ryegrass before it ever establishes. Geoff Reeves walks through the chemistry behind its staying power and lays out a two-pass overlapping residual program built to draw down the seedbank and keep this chemistry working. In this episode: Killing it in the crack. Pyroxasulfone shuts down very-long-chain fatty acid (VLCFA) elongases in germinating seedlings before the shoot ever reaches daylight — which is exactly why it does nothing to ryegrass that's already up. Low rate, tight binding. It runs at roughly one-eighth the rate of the older chloroacetamides. High enzyme-binding affinity, low water solubility, and moderate soil binding are what stretch the residual window. Two passes, overlapped. A fall application — late October into November — with a burndown partner like glufosinate, followed by an overlapping pass around February to catch the spring flush. No water, no herbicide. You need 0.5 to 0.75 inches of rain to activate it. Sitting dry on the surface, it lets ryegrass through even though the product is right there. Where resistance actually comes from. Target-site resistance is rare here. The real risk is the declining low-dose tail at the end of the residual window, which selects for metabolic, GST-based resistance. Full label rates and zero tolerance for seed-set on escapes are what keep the seedbank shrinking. Rotation and cover crops. Fitting winter peas, crimson clover, or cereal rye into the program for added ryegrass suppression — without boxing yourself in on the next cash crop or blowing through seasonal rate limits.