Weed Management in Double-Crop Soybeans
Posted: June 19, 2012
This results in fewer weeds emerging, but when they are present, the combination of weed competition and potential dry weather can greatly impact yield potential. A weed-free start is one of the most critical aspects of weed management in double-crop soybean. One of the biggest weed concerns in is managing glyphosate-resistant marestail or horseweed. Some of these populations may also be ALS-resistant. Marestail that are cut off during small grain harvest will recover, branch out, and probably be even more difficult to control. In full season soybeans, we have been strongly advocating the use of 2,4-DLVE in the burndown program. However, most growers are not willing to wait the necessary 7 days after 2,4-D application in double-crop. So, what are the options?
- For glyphosate susceptible maretail, apply glyphosate at 1.5 lb ae/A (44 fl oz of Roundup PowerMax, 48 fl oz or Touchdown Total or Durango DMA or 64 fl oz of a 3 lb ae/gal product).
- Include 1 pt per acre 2,4-DLVE in the burndown and wait 7 days to plant.
- Add 1 oz of Sharpen (or equivalent rates of Optill or Verdict) to glyphosate.
- Add FirstRate (or Authority First or Sonic) or a chlorimuron containing product (Authority XL, Canopy, Envive, Synchrony, Valor XLT, etc.) to improve control if the population is not ALS-resistant.
- Use Ignite or Liberty at 29 to 36 fl oz in the burndown application. This is fairly good on marestail, but not that effective on some other weeds such as large annual grasses and Canada thistle. You can tank-mix with other herbicides to improve performance and provide residual control (Sharpen, metribuzin, etc.)
- Plant a LibertyLink soybean and apply Ignite or Liberty POST as needed.
- Plant a Roundup Ready soybean and apply glyphosate POST if marestail is not a problem.
- For growers interested in nonGMO soybeans, a number of POST herbicides are still available, but many of the broadleaf products have some potential for soybean injury and they are not effective for control of marestail.
- Weed Science