We have seen a number of new soil applied soybean herbicide products come into the market place over the last few years.
Most of these are new mixtures of active ingredients found in other products although a few such as Sharpen (saflufenacil) are new active ingredients.
Unlike some areas of the U.S., most Pennsylvania farmers that grow soybeans have fortunately had fairly diverse rotations that include corn, small grains, Roundup Ready and conventional crops, maybe alfalfa or other types of hay and probably some tillage helping to diversify the weed management program.
Herbicide resistant weeds, and in some cases no-till, are driving the adoption of residual herbicides. Some northeastern farmers certainly do and would benefit from residual herbicide programs in soybeans. So, where do they make the most sense?
Here is our list:
• Long-term, continuous no-till where reliance on herbicides is greater than where tillage is used is a prime candidate.
• Roundup Ready crops: This becomes even more important in continuous Roundup Ready soybeans and corn which often depend heavily on glyphosate for weed control. This is where horseweed/marestail is a problem in soybean and glyphosate alone will NOT work.
• Wide-row soybeans can benefit from a residual herbicide in combination with a single well-timed post application. This helps suppress the weeds early in the summer and the post application cleans things up.
• Perennial weeds: With problem perennials like Canada thistle, pokeweed, hemp dogbane, or other problem perennials, glyphosate applied to the perennial weeds at the bud to bloom stage will have the biggest bang for the buck (or better yet in the fall). Control the annual weeds with the soil- applied residual program to allow for the slightly later more optimum post application targeting the perennials.
• If you routinely have problems controlling annual weeds because of high severity, prolonged germination pattern, or other reasons with a single in-crop application, then a soil applied program can make sense.
• If you are unfortunate enough to be dealing with glyphosate resistant or tolerant weeds like horseweed (marestail), ragweed, or lambsquarters, then a soil residual program will help this effort. This can also be true for ALS-resistant weeds like shattercane, pigweed, and foxtail.
• Finally, a soil residual program can definitely provide some insurance and lessen the workload when weather and tight spray schedules are frequently a problem in making a well timed application.
So, as you prepare to plant that soybean crop, consider where residual programs make the most sense and choose the program for good reason(s).
(Even with new herbicide products coming along, an old reliable may be making a comeback. For that, visit http://southeastfarmpress.com/management/can-24-d-solve-weed-resistance-problem and http://southeastfarmpress.com/soybeans/research-findings-could-be-important-24-d-resistant-soybeans).