Cotton growers can look forward to more tools for weed and insect control from new technologies that have been in trials for several years and are now moving toward commercialization.
In most cases, Mississippi State University Extension specialists say they have been working with these technologies under confidentiality agreements and have not been able to discuss them until now.
One technology — Bollgard II XtendFlex cotton, a triple-stack variety from Monsanto with tolerance to dicamba, glyphosate and glufosinate herbicides — is estimated to be planted on 750,000 acres across the cotton belt this year, says Darrin Dodds, MSU associate professor of plant and soil sciences.
EPA deregulated the Xtend trait in time for cotton plantings, but approval for over-the-top application of dicamba is still pending and the herbicide cannot legally be used on cotton this year. It is expected that registration will be granted in 2016.
Tolerance to three unique modes of action in the Xtend system will provide added choice and flexibility to apply multiple combinations of these three herbicides pre- or post-plant for a very effective weed management system, Dodds says.
The Enlist Weed Control System from Dow AgroSciences builds on the Roundup Ready system by incorporating tolerance to a new 2,4-D formulation.
Enlist Duo herbicide combines glyphosate and a new 2,4-D aimed at tough broadleaf weeds. Tolerance to 2,4-D means fewer plant-back restrictions; growers can plant Enlist crops immediately after applying 2,4-D for burndown.
To use Xtend or Enlist, Dodds says growers will have to complete an online training module. "Also, when applying these materials, it will be important to use specific spray tips and boom height." Applications cannot be made in winds exceeding 10 mph. Growers will need to carry out "a rigorous cleanliness regime for tanks, hoses, etc. The label will have the final word on these requirements."
He also cautions: "Keep in mind that Xtend and Enlist are two different chemistries — they are not interchangeable."
Pigweed (Palmer amaranth) is "the driving factor in weed control today," says Jason Bond, Extension professor at the Delta Research and Extension Center, Stoneville.
But he says, there are now nine confirmed glyphosate-resistant weed species in Mississippi — more than any other state.
"Palmer amaranth is more concentrated in the Delta," Bond says, "but there is no area of the state that doesn't have some of it. Waterhemp is another weed that we can pretty much assume is glyphosate-resistant. If these weeds are in your county or surrounding counties, the way these species move, it's likely you will sooner or later have resistance. We're not recommending any weed management program that doesn't include both preemerge and postemerge herbicides.
"These new systems, Xtend and Enlist, will be added to our MSU recommendations. The nuts and bolts of our weed control recommendations will remain the same — with variations according to your choice of technology."
Since the advent of Bt cotton, registrations have stipulated that companies must continue developing the technology to avoid resistance and improve efficacy. So, companies are continuing to add other genes in the mix to manage resistance.
"The real value of all Bt cotton has been tobacco budworm control," says Jason Gore, MSU associate professor of entomology and plant pathology. "Bollgard I represented a huge advance over non-Bt cotton. Bollgard II added more options. The third generation of Bt cotton is not as big an improvement as Bollgard II was over Bollgard I, but in tobacco budworm country, it is valuable from a resistance management standpoint, and growers will welcome this new technology."
Another technology in the pipeline is cotton with a gene for plant bug control. While that in itself may not have been enough to warrant commercialization, says Gore, there was a surprising corollary benefit that could result in the technology coming to market — thrips control.
The gene targets adult and immature plant bugs, he says, but even though it offers effective control, "we probably will still have to spray in areas with high populations, such as the Delta, where growers can now make as many as 10 applications in a season. This technology could very well reduce the number of applications by 50% or more."
Although the plant bug gene might not have been of sufficient demand across the cotton belt to justify its commercialization, Gore says, "we noticed in our research that we were also getting thrips control from this trait. A gene for thrips control is something that could be applicable to almost every cotton acre in the U.S."
Brandon is editorial director for our sister publication Delta Farm Press.