Mark Loux
A recent change to the Sharpen label results in more utility for this product in spring burndown programs for soybeans. Sharpen can now be applied in a mixture with other PPO-containing herbicides, as long as the following conditions are met: applied at least 14 days before soybean planting; soils are medium to fine-textured; or soils are coarse-textured soils but have 2% or higher organic matter. This pertains to any product containing flumioxazin (Valor, Valor XLT, Envive, etc), sulfentrazone (Authority products, Sonic), and fomesafen (Prefix, Vise). The Sharpen label previously allowed these mixtures only when applied at least 30 days before planting. Labels for most of the PPO-containing residual herbicides appear to also be changing to recommend mixtures with Sharpen at least 14 days before planting. These labels refer the user to the Sharpen label for specifics on timing, rate, soil type, etc.
So what’s the broader picture on Sharpen use in spring burndown programs? Or as one agronomist asked – if I have to wait 14 days to plant when I apply a mixture of Sharpen with a Valor or Authority product, what’s the advantage compared with using a mixture of a Valor or Authority product with 2,4-D and some additional metribuzin? Good question although it may miss the point somewhat. This is not necessarily an either/or situation. One of the common problems in marestail control programs is the variable effectiveness of the spring burndown in fields that were not treated with herbicide the previous fall. Variability in control generally increases as the spring progresses and marestail plants become larger and older, and environmental conditions play a role also. So there can be an advantage to mixing Sharpen with an already comprehensive herbicide program to try to minimize this variability. Even the lowest rate of Sharpen can provide some additional residual control, and there are certainly some fields where applicators try to avoid the use of 2,4-D due to neighboring gardens, vineyards, greenhouses, etc.
Our main problem with the new label is that it doesn’t go far enough, and allows only the 1-oz rate of Sharpen in mixtures with PPO herbicides. Increasing the Sharpen rate can substantially increase the help it provides with residual control of marestail, and this is still possible only when using a metribuzin-based program. When applied 14 days before planting, the 1.5-oz rate of Sharpen can be used in combinations with metribuzin, Canopy DF, Matador, Boundary, etc, following the same soil type restrictions listed in the first paragraph. The 2-oz rate can be used 30 days before planting. BASF is apparently still working out how to label the higher rates with PPO herbicides, but we have been told that we could possibly see this sometime in the future.
Source : osu.edu