Dr. Mark Loux, Ohio State University
There are still some tough burndown situations in the state due to weeks of less than ideal weather conditions.Controlling large marestail is probably the biggest challenge, especially when there's not much time between herbicide application and soybean planting. This situation is discussed in the video below. We realized too late however that while we showed examples of areas where marestail were still alive following an early burndown, we didn't cover what the options were for a second burndown to control these and newly emerging plants where soybeans have yet to be planted. Options here depend upon what was already applied earlier in spring. Where a mixture of glyphosate, 2,4-D and residual herbicides was applied early, a follow up burndown of Sharpen plus glyphosate or glufosinate or Gramoxone would be adequate to control the marestail and small grasses and ragweeds that have emerged. It's probably possible to just apply Gramoxone or glufosinate in these situations, along with a few ounces of metribuzin. Where residual herbicides were applied early, it may also be beneficial to include another reduced rate of residuals in any second burndown. This can improve the chances of: 1) controlling marestail until the soybean canopy can take over and provide late-season control; and 2) controlling giant ragweed, grasses, and other weeds until soybeans get somewhat established and the POST herbicides can be applied.
Dr. Mark Loux provides suggestions for control of big marestail in late burndown situations.