The Fickle Fate of Mother Nature
August 20, 2009 Mother Nature is fickle, and this year she proved once again just how much. This year’s cotton crop across the Belt is off to a slow start, whether it be from heavy rain or severe drought.
“We had a pretty tough planting season and we had a lot of fields that had to be replanted,” says Dr. Walt Mullins, Monsanto cotton traits technology development manager. “What this has resulted in, in a lot of cases, are fields that have different growth stages. Some of that is due to spot planting and replanting that complicates application of Roundup over the top of Roundup Ready cotton because of the limitations of applying it before four true leaves or earlier. At five true leaves, it gets a little iffy. Growers have to be very careful if they believe they are past that fourth-leaf stage.”
None of that will apply to Roundup Ready Flex varieties. “This will be a year where Roundup Ready Flex solves a few problems for growers in terms of application windows,” Mullins adds.
Dr. Wayne Keeling, Professor and Systems Agronomist at the Texas AgriLife Research Center in Lubbock, agrees that Flex varieties will have an advantage over regular Roundup Ready varieties. “Once we get to August, the two main weed species we’re going to have problems with are going to be Palmer amaranth and morning glories. With Flex cotton, people can deal with Palmer amaranth a lot better than they could with just the regular Roundup Ready. If there are weeds sticking out above the canopy, they can spray at any time.”
Bayer CropScience has its Liberty Link trait in some of its FiberMax varieties, making them tolerant to the non-selective, glufosinate-based herbicide Ignite.
“Even with a late crop specifically, there’s not a lot different in terms of application techniques or timing,” says Andy Hurst, Bayer product manager for Liberty Link and Ignite. “Obviously we recommend timely postemerge applications of Ignite, then as needed.”
The publication “The First 40 Days, Fruiting to Finish” supports that, and states a common mistake growers make is applying a herbicide based on crop stage and not weed size. That may be more important this year than ever.
“I would add that with Ignite, there’s the flexibility to use it as a hooded-sprayer application in non-Liberty Link and Roundup Ready cotton for escapes,” Hurst adds, “particularly on weeds with glyphosate issues – pigweed, marestail.”
Remember Residuals?
A recurring theme among the weed scientists on the tours and field days of 2008 was to look back at the successful weed-control programs of the mid-90s. Remember tank mixes with alternate chemistries with different modes of actions? Well, remember them again.
The point being that there was no one chemistry that controlled every weed species normally present in a particular field. What field didn’t have a mixture of broadleafs and grasses? Not many.
While Monsanto’s Roundup is arguably the most revolutionary herbicide in history and most popular glyphosate product, Roundup after Roundup after Roundup has caused some weeds to become tolerant or resistant. Everyone already knows the lyrics to the glyphosate-resistant Palmer amaranth and marestail tunes. But on top of that, other weed species are starting to show signs of resistance. And on top of even that, resistance to ALS inhibitors is being confirmed. Here comes Mother Nature again, and resistance is just her way.
To put it succinctly, Mississippi Extension Cotton specialist Dr. Darrin Dodds says, “I tell my guys that if we have Palmer amaranth issues, or even think we do, I would absolutely get a residual in the mix. In Mississippi, if I talk to a grower about marestail, I consider it resistant because it’s not worth taking a chance.”
Keeling says that although West Texas has not had the resistance problems of the Mid-South and Southeast, that does not mean it’s insulated.
“We haven’t seen any resistance problems yet, but that’s why we tell people to keep using the residual products with different modes of actions so that, hopefully, we can avoid those problems,” he explains.
Keeling mentions residual herbicides such as Staple, Dual or Prowl H2O in tank mixes with glyphosate. “Those will certainly help when mixed with Roundup to give residual control to reduce late-season Palmer amaranth germination. From a morningglory standpoint, Staple would be the main option. Morningglory is probably the one that’s giving us the most problem throughout the season, but certainly late season ― especially where there’s irrigation and the morningglories are still growing.
“Over-the-top or post-direct is where they may want to add a product like Direx, Caparol or Layby Pro with Roundup,” he adds.
Monsanto saw the need for adding a residual herbicide to the mix for better weed contol and to protect the efficacy of Roundup several years ago by introducing PARRLAY, a metolachlor-based herbicide.
This year, through its Roundup Ready Cotton Performance program in the Mid-South and Southeast, Monsanto offered rebates on the preplant residuals Valor, Reflex and Cotoran. Monsanto is still offering rebates on the early post products PARRLAY and Dual Magnum, and the layby product Direx.
And Monsanto warns that all glyphosate products are not created equal.
“We routinely check our competition to see what type of product they’re selling, what type of surfactant they’re using and what other components they have in their formulations,” says Joe Sandbrink, Roundup technology development manager. “We discovered early this year that there were a number of products that we tested that contained a component or an impurity in the formulation that can cause crop injury to Roundup Ready cotton.”
Add 2 captions to 3 photos:
Palmer amaranth and marestail not only compete with cotton, but can out grow it.
Many weed scientists are recommending post-directed sprays with glyphosate and a residual herbicide.
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