Planning ahead for weed control in RR soybeans
Fall harvest is a good time for producers to assess the weed problems they had in soybean fields this year, to plan a good weed control program for next year. In many cases, it is no longer possible to rely strictly on glyphosate for broadleaf weed control in Roundup Ready soybeans. Before deciding which other herbicides should be used in addition to glyphosate, it is necessary to know what weeds are being targeted. Some good options for the most common broadleaf weed and grass problems include:
* Pigweeds (including waterhemp and Palmer amaranth). Glyphosate-resistant waterhemp appears to have exploded across eastern Kansas during the last two years. Glyphosate-resistant Palmer amaranth has not yet been confirmed in Kansas, but is a major problem in the southeastern U.S. For early-season pigweed control, the Valor-based herbicides (Valor SX, Valor XLT, Fierce, Gangster, Envive, and Enlite) and Authority-based herbicides (Authority XL, Authority First, Sonic, Authority Assist, Authority MTZ, and Spartan) can all provide very good to excellent control to supplement a postemergence glyphosate program. Prefix is another excellent “foundation” herbicide for residual pigweed control in soybeans. Intrro, Dual, Outlook, and Prowl products can also provide some early-season pigweed control, but generally are not as effective as those previously mentioned products. Although some of these herbicides can be applied in the fall or early spring, those treatments generally will not persist long enough to give good pigweed control into the soybean growing season. So, if pigweed is the primary target to control, treatments will be most effective if applied no more than two weeks prior to planting.
* Velvetleaf. Glyphosate is not always entirely effective on velvetleaf. To assist in velvetleaf control, the Valor-based and FirstRate-based herbicides (Valor SX, Valor XLT, Fierce, Gangster, Authority First, and Sonic) are some of the most effective preplant and preemergence herbicides you can use.
* Cocklebur. The most effective preplant and preemergence herbicides to aid in cocklebur control are those that contain First Rate, Classic, or Scepter. Such products would include Authority First, Sonic, Gangster, Envive, and Valor XLT. Extreme, which is a premix of glyphosate and Pursuit, can also be used as a preplant or postemergence treatment in Roundup Ready soybeans to provide residual cocklebur control. However, all of these herbicides are ALS-inhibiting herbicides, and ALS-resistant cocklebur may be present in some fields.