Control of marestail in no-till soybeans
• The addition of dicamba to early spring burndown treatments can improve control or emerged marestail, especially plants that have overwintered. Dicamba can be more effective than 2,4-D on marestail in the spring, but has more potential to injure soybeans if the recrop guidelines are not followed. Following dicamba application, soybeans can be planted 14 to 28 days after an inch of rain has occurred (in total). For example, the Clarity label states the following - “following application of Clarity and a minimum accumulation of one inch of rain, a waiting interval of 14 days is required for rates of 8 oz/A or less.
3. Include residual herbicides with the burndown treatment. Add one of the following herbicides or herbicide combinations to the burndown herbicides, for residual control of marestail until the soybean leaf canopy develops.
- Valor, Valor XLT, Envive, Enlite, Fierce, or Gangster
- Authority First, Sonic, Authority XL, Authority Broadleaf, Authority Assist, Authorit Maxx, or Spartan
- Metribuzin - Metri DF, Tricor, etc (at least 8 oz/A, and preferably 10 to 12 oz/A), but do not exceed recommended rate for soil type per the label.
- Add metribuzin to other metribuzin-containing products to bring total metribuzin rate to 0.38 to 0.5 lbs ai/A. Products here include: Boundary/Ledger, Canopy/Cloak DF, Intimidator, Matador, Authority MTZ.
- Most consistent control of ALS-resistant populations will occur with rates of these products that maximize the amount of the non-ALS component - flumioxazin, sulfentrazone, or metribuzin.
- Consider adding 4 to 6 oz/A of metribuzin to products that contain flumioxazin or sulfentrazone to improve burndown and residual control. In OSU research, this has been a more consistent approach than relying on any one herbicide.
- Where early spring application is needed due to lack of a treatment the previous fall, increase herbicide rates and consider more complex mixtures (or consider split spring approach - see below). Adding metribuzin to other products can help. Sharpen can be added to early spring treatments of metribuzin to improve residual control, especially at the 1.5 to 2 oz/A rate. These rates must be applied 14 to 44 days before soybean planting, depending upon rate and soil type.
4. No fall treatment? - consider split-spring applications. Failing to treat fields in the fall can result in a population of overwintered marestail plants the following spring, which should be controlled early in spring to ensure effective burndown. Applying all of the burndown and residual herbicide early can result in poor control of plants that emerge mid-season. An alternative approach is to apply burndown herbicides with some of the residual herbicide in early spring, and then when soybeans are planted, apply the rest of the residual herbicide. The second application may require some additional burndown herbicide. Examples here include:
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