Southeastern peanut growers will have several new products to choose from for the 2001 production season, including a long-awaited broadleaf herbicide and a plant growth regulator.
The Environmental Protection Agency approved the use of the herbicide flumioxazin or Valor in April — just in time for this year's crop. Valor, which is produced by Valent U.S.A., is especially effective against Florida beggarweed — the primary weed problem in Southeastern peanut fields.
Valor is a 51-percent WDG formulation with a recommended use rate of three ounces per acre, says Eric Prostko, University of Georgia Extension weed scientist. The labeled rate is two to three ounces per acre, but Georgia is recommending three ounces for controlling Florida beggarweed, says Prostko.
Do not incorporate
“Another key point to remember about Valor is that it's a pre-emergence herbicide. It should not be incorporated, and it should be applied within three days of planting. If you exceed the three-day planting window, you possibly could get crop injury. If the peanuts are even remotely close to cracking, you don't want to put out Valor because it'll burn the peanuts. Ideally, Valor should be put out immediately after planting and watered in with irrigation,” he says.
Valor's mode of action can be described as a “cell membrane disrupter,” notes Prostko. “This mode of action is similar to other products in peanuts such as Blazer. Valor is not an ALS inhibitor like Cadre, Strongarm, Pursuit and Classic. It hasn't been over-used in any crops.
“There are no rotation restrictions for this herbicide. One of our biggest issues in Georgia is planting cotton after peanuts, and that's not a problem with Valor. This herbicide also won't cause any problems if you're planting corn or vegetable crops.”
Growers can expect about four to six weeks of residual control from Valor for most broadleaf weeds under optimum conditions, says Prostko. For Florida beggarweed, residual control should be closer to six to eight weeks, he adds.
“In some of our research, we've seen full-season beggarweed control. It depends on how severe the weed problem might be. In the Southeast, many of our fields have extremely high beggarweed populations. Using Valor won't guarantee that you'll never see another beggarweed, but it's the most consistent product we've seen against beggarweed in peanuts,” he says.
Valor also is effective against tropic croton in peanuts, says Prostko. The herbicide's weaknesses include purple and yellow nutsedge and cocklebur, he says.
At the three-ounce rate, Valor will cost about $15 to $16 per acre, he notes. “This product will be a good option for those growers who are having problems controlling beggarweeds in their peanut fields. It'll also work for those growers who need general broadleaf weed control, and who don't want to worry about rotation restrictions. This product offers flexibility to those peanut farmers who also grow vegetables.”
Valor also is labeled for use on soybeans, and it's been proven effective against lambsquarters, morningglory and prickly sida.
It's been several years since peanut growers had a plant growth regulator, but that'll change in 2001. The BASF Corp. has received a label for using the active ingredient prohexadione calcium on peanuts.
This plant growth regulator will control vine growth by reducing internode length. The result will be a more compact plant that provides better row definition. The trade name for the material, which is labeled for peanuts and apples, is Apogee.
University of Georgia Extension Peanut Specialist John Beasley has been working with the plant growth regulator in field trials since 1996. “We started looking at the effect of the material on different cultivars. We also looked at the timing of applications, particularly as it relates to twin rows versus single rows,” says Beasley.
During initial testing of the product, research protocols called for making the first application when 50 percent of the rows were touching in the middle, he says. A second application would be made about two to three weeks later, he adds.
But twin-row peanuts lap faster than single rows, says Beasley. “If you're basing that first application on when the vines begin to touch, then the twin rows will touch three to four weeks earlier than the single rows. We wanted to see if that was too early to make an application,” he says.
Researchers also looked at the tank-mix compatibility of the growth regulator, he says. “We looked at tank-mixes with herbicides, fungicides and insecticides. We wanted to make sure we could use this product with other chemicals.”
In university trials, the product did control vine growth, reports Beasley. “In most cases, we saw a significant reduction in vine growth. We were measuring main stem height late in the season because plant physiologists say that is one way to get a true indication of vine growth reduction.
“In most cases, on most cultivars tested in the past five to six years, we did see a reduction in main stem height, and this indicates an overall reduction in vine growth.”
Researchers in North Carolina, using Virginia varieties, evaluated the product in terms of row definition, says Beasley. Virginia peanuts have a more upright growth habit than the runner cultivars used in the Southeast, he explains.
“We tried doing that, but our runner peanuts tended to lap up. But we were able to see, in a side-by-side comparison, some definite vine reduction.”
No significant differences were seen in yield and grade where the plant growth regulator was used, says the agronomist. “In some years, we could see the rows better and thereby be more efficient in our harvesting. The reduction in vine growth will help those producers who have fields with high fertility levels and irrigation. There should be no rotation restrictions with this material.”
The plant growth regulator also mixes well with other chemicals, says Beasley. The product performed equally well when tank-mixed with herbicides, fungicides or insecticides, he adds.
It's recommended that one quart per acre of a liquid nitrogen material and one quart per acre of a crop oil concentrate be used with each application of the plant growth regulator, he says. This will help to move the material into the plant tissue and through the leaf cuticle, he adds.
“It's recommended that the first application be made when 50-percent row closure has been accomplished. This will occur much quicker with twin rows, but we didn't see a difference in the efficacy of the product. A second application is made two to three weeks later. A third application may be required, but we always worked with two applications.”
Benefit the most
Growers who use high seeding rates and high fertility levels will benefit most from using a plant growth regulator, says Beasley. The product may be beneficial regardless of the variety being planted, he adds.
Peanut producers also will see new options for controlling diseases this year. Stratego, which will be marketed by Bayer, is a twin-pack product, says Tim Brenneman, University of Georgia plant pathologist.
“Part of the combination is Tilt, and the other is a new chemical material — trifloxystrobin — that is in the same class of compounds as Abound, but has a different range of activity.
“In fact, trifloxystrobin is labeled for leafspot, rust and web blotch. These are all foliar diseases. It doesn't have activity on white mold or stem rot,” says Brenneman.
A label change this year now means that Abound fungicide can be used in-furrow. Also, it can be used up until 14 days prior to harvest.
There's an increased interest among some growers for using in-furrow fungicides in peanuts, notes Brenneman. “We've looked at a number of trials where we get about a 200-pound-per-acre increase in yield from using an in-furrow fungicide.
“We've seen increases as high as 1,000 pounds. And, in other trials, we've seen no response. There are a number of benefits, including stand insurance. There's evidence of controlling soil-borne diseases, particularly aspergillus crown rot.
“There's also evidence of early season white mold control. An in-furrow treatment could offer suppression until you can get back in the field with a postemergence spray. Basically, it's insurance, and it'll cost about $10 per acre,” says Brenneman.