Post Emergent Herbicide Spraying for Sunflowers
There are limited choices for post emergent herbicides for sunflowers and the window is small. Understanding how to stage sunflowers will help you to not get caught off guard and apply your post emergent herbicide on time.
Factors to Consider
- The early stages are considered vegetative and start with a “V”, followed by the number of leaves.
- When first emerging out of the ground, that is considered Vegetative Emergence (VE).
- Staging sunflowers in the vegetative stages is done by counting “true” leaves, pointed and 1.5 inches long.
- Sunflowers put on two leaves at a time (V2, V4, V6, etc).
- Post weed control options allow spraying up through V8 stage.
- Growing degree days (GDD) for sunflower have lower end (44 vs 50 degree F) and higher end (no top end vs 86 degree F) than corn.
Action Plan
Plants with the ExpressSun® trait can be sprayed from V2 to pre-bud (safe bet to have it on by V10).
- Express herbicide with Totalsol is the cemical used (tribenuron methyl)
- Up to 1 oz/acre, per growing season (0.25-0.5 oz/application)
- Large application window (2 leaf to pre-bud)
- One pass control for broadleaf
- Good to excellent Canadian thistle control, poor control of cocklebur
- Group 2 herbicide (ALS) = kochia is resistant
- A grass control herbicide needed to tank mix with Express to control grasses, antagonism of Express requires approximately 50% more grass herbicide rate than if grass herbicide was applied alone
The Clearfield® trait can be sprayed from V2-V8 with the Beyond herbicide at 4 oz per acre.
- Beyond Extra® is the chemical used
- 4 oz/acre plus NIS at 1 quart/100 gallons (.25% v/v) + AMS 12-15 lbs/100 gallons
- Large application window (V2-V8 stage)
- One pass control for broadleaf and grass, tank mix grass herbicide for consistent control of grasses, one application per growing season
- Good to excellent cocklebur control
- Up to 4 weeks residual activity under ideal conditions
- Crop Rotation restrictions to be managed after application factors include rainfall, soil type, and pH
- Good control of Lance Leaf Sage is a strength vs. Express in the west
If you have Nufarms’s Clearfield Plus hybrid, N4H470 CLP, you can tank-mix in a methylated seed oil instead of non-ionic surfactant for a better weed kill.
- Beyond Extra® is the chemical used
- 4-6 oz/acre (adjuvant MSA 1% or HSOC @ 0.5% v/v) plus 12-15 lbs AMS or 2.5 gallons UAN/100 gallons water equals greater efficacy than NIS
- Large application window (V2-V8 leaf stage)
- One pass control for broadleaf and grass, tank mix grass control herbicide for consistent control of grasses, on application per grower season
- Good to excellent cocklebur control
- Up to 4 weeds residual activity under idea conditions
- Crop rotation limitations in low rainfall and high pH situations
- Group 2 herbicide (ALS) = kocia is resistant
Zidua® is also labeled post-emerge, V2-V8, for residual control (needs to rain to activate).
With all of these products, consult your local agronomist or the label for proper rates and adjuvants.
