The number of calls I get on sunflower weed control since I started with the Arkansas Extension Service two years ago has been a big surprise to me. Most are from folks who work in agriculture and have a pretty good idea about weed control and growing crops. However, some are from people who are only trying to grow sunflowers for doves and do not farm or consult for a living.
Many callers want to know how to control broadleaf weeds in sunflowers. Since sunflowers are considered weeds in many crops, most broadleaf herbicides control them. Some (mainly cotton) products, however, have been used “off-label.”
Because sunflowers grown for doves are not harvested or sold, many people think they can use whatever herbicide they want on them. I work closely with people on the Arkansas State Plant Board, and they assure me that this is not the case.
Even though the sunflowers are destroyed at the end of the season, it is a violation of federal and state law to use products not specifically labeled for sunflowers. Needless to say, I have been very hesitant to make “off-label” recommendations.
Until this past year, dove hunters could use Prowl or Dual as a pre-emerge treatment to control grass and some small-seeded broadleaf weeds in sunflowers. A follow-up treatment of Select herbicide could be used for escaped grass, mainly johnsongrass.
A legal broadleaf treatment, however, was not available. This year, FMC introduced Spartan herbicide for broadleaf weed control in sunflowers, and BASF received a Section 3 label for Beyond herbicide use in Clearfield sunflowers.
Spartan contains the active ingredient sulfentrazone (also known as Authority). In our trials, Spartan has provided good control of morningglory, cocklebur and several other troublesome broadleaf weeds. FMC estimates that enough Spartan was sold this year in Arkansas to treat around 3,500 acres of sunflowers, a number which likely will increase next year.
Ken Smith, John Boyd and I added a sunflower weed control section to our MP-44 Recommended Chemicals for weed and brush control. The sunflower section of the publication has been such a hit this year that we may have to increase the number of MP-44s that we produce.
In my research program, Prowl or Dual tank-mixed with Spartan provided a broad spectrum of grass and broadleaf weed control and has become my favorite recommendation for sunflowers. The best thing is that it is legal to recommend and use. The program continues to look good in my plots this year. The treatment was followed by Select at 8 ounces per acre for johnsongrass.
Several folks went out of state and brought in some Clearfield sunflowers for this year. I think it was due to their experience with Newpath in Clearfield Rice. However, Newpath is not labeled for use in Clearfield sunflowers. The only herbicide from that family (imadazolinone) labeled for use in Clearfield sunflowers is Beyond.
We looked at Beyond in Clearfield sunflowers a little last year and have two trials this year. Labeled for use in Clearfield sunflowers, wheat and canola, it contains the active ingredient imazamox, also marketed in soybeans as Raptor. This product is available for use as a salvage treatment in Clearfield rice for escaped red rice to prevent out-crossing under a special state 24C label.
Beyond has both grass and broadleaf activity and is for post applications only.
Beyond has almost no soil activity. In our research, a pre application of Spartan, followed by a Beyond application, is still needed for our Southern weed spectrum if you are going to use Clearfield sunflowers.
Several critics have asked me why weed control in sunflowers is important if all you are going to do is mow them down (always follow game and fish regulations) at the end of the season. I can think of a few reasons.
First, if you do not have dogs, weed control can make it easier to find a dove (if you are a better shot than I and can actually knock one down).
Second, most people grow sunflowers in marginal areas with low fertility and no irrigation. Weeds can greatly reduce the number of sunflower seeds produced and reduce the benefit to doves.
If weeds are left uncontrolled and sunflowers are grown in the same areas over and over, the problem gets progressively worse each year and the value of a lease for sunflowers or the value of leased hunts is greatly reduced.
Our sunflower research program is funded in part by BASF and FMC. Their support of sportsman activities in Arkansas is greatly appreciated.
Bob Scott is the University of Arkansas Extension weed specialist. firstname.lastname@example.org.