As resistance continues to develop to widely-used pesticides, growers need to be vigilant in protecting the chemistries now available, says Darrin Dodds.
“I never like to see us lose options, because new compounds don’t come along very often,” he said at the joint annual meeting of the Mississippi Boll Weevil Management Corporation and the Mississippi Farm Bureau Federation Cotton Policy Committee. “This year marks the tenth summer I’ve been doing this work, and during that period I’ve seen just one new active ingredient come to market."
Dodds, who is associate Extension/research professor of plant and soil sciences at Mississippi State University, says development costs for a new pesticide and ever-stricter registration requirements make it increasingly challenging for companies to go through the lengthy process of getting a new product into the farmer’s hands.
“Transform probably had one of the best toxicity packages of any insecticide that that we’ve seen in a long while, and we’re still having issues with maintaining registration in order to protect non-target species.
“I’m told it now costs $350 million to $400 million to develop a new product. If you think about a $400 million investment, with no guarantee of a return on that product, it’s a pretty risky venture, not to mention all the difficulty in making it happen.”
The dearth of new materials in the pipeline makes it important, Dodds says, that growers not do anything to jeopardize the materials and technologies they now have.
“We all understand the potential drawbacks of the phenoxy technologies, particularly with regard to off-target applications in neighboring fields. And issues are developing that we hadn’t thought of.”
An example, he says, are reports about phenoxy contamination in mini-bulk tanks — “growers putting a phenoxy herbicide in a mini-bulk tank and then refilling that tank with another pesticide and getting crop injury. If the tank isn’t thoroughly cleaned, it doesn’t take much phenoxy residue to cause injury.”
Spray droplet size important
With the new technologies, Dodds says, more emphasis will be placed on droplet size in spray applications. “Angus Catchot [Mississippi State University Extension professor of entomology] and I are working on this with some of our students, looking at the impact of droplet size for insecticides, herbicides, and harvest aids.
“With all of the issues surrounding pollinator protection, there is a fairly strong school of thought that we’ll start seeing product labels — particularly insecticides —with restrictions on droplet size.”
It’s not the easiest thing in the world to monitor droplet size, he says. “It can change with spray tip, sprayer pressure, volume of material being applied, and with the material itself.
“We’re working very closely with Greg Kruger at the University of Nebraska to determine how various droplet sizes impact control of thrips, plant bugs, pigweed, etc. We want to find the happy medium of keeping the material on target, while optimizing control with these expensive materials.”
MSU specialists are continuing numerous research projects, Dodds says, to evaluate new technologies in the pipeline from the standpoint of yield performance, how well Bt traits stand up to worms, the differing tolerance levels of varieties to herbicide combinations, etc. “We have about 50 different varieties in our OVT trials, looking at which ones tend to be more tolerant to herbicide combinations.”
Work is also continuing on development of a best management practices program for plant bugs, he says. Among recommendations: “The first is to plant early, which seems to limit the time plants are exposed to plant bugs. Planting early varieties also is a factor. And hairy varieties don’t seem to be as susceptible to plant bug injury as some smooth leaf varieties.
“Stoneville 5288, which was a very hairy cotton, is a good example of a variety that appears less susceptible to plant bugs. We understand, also, the ramifications of hairy varieties in the ginning process, and we’re looking to that.
Impact of nitrogen rates
“We’re also doing large scale work to determine how nitrogen rate impacts plant bug infestations and subsequent yield. For years, the standard in Delta cotton has been 120 pounds of nitrogen, 90 pounds to 100 pounds in the hills. But our work over the years has indicated yields in the Delta are maximized at 80 pounds.
“When I tell growers who irrigate that 80 pounds to 90 pounds is adequate, they kinda shake their heads. But consider: If you cut back from 120 pounds to 90 pounds and still maximize yield, you’ve just saved 25 percent on nitrogen costs. Then if you can eliminate just one plant bug application as a result of the change in nitrogen rate, you’re putting more money back in your pocket. With 62 cent or 63 cent cotton, if we can show you changes that will make you more efficient and save money in the process, it makes us happy.”
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Although Mississippi cotton acreage has been well below historic norms in recent years, Dodds says yields have been outstanding.
“Last year, the USDA report shows Mississippi’s average at 1,024 pounds. In 2013, 2014, and 2015, we either had record yields or tied a record [2004 tied the 2015 yield]. We’ve been very fortunate the last three years to make really, really good yields despite some late starts, and I’m hoping this year will continue that trend.”
Despite a “difficult and challenging spring,” Dodds says, Mississippi producers planted 41 percent more cotton this year than in 2015, with USDA pegging acreage at 450,000. “We’re third in the nation in acres, behind Texas and Georgia. Historically, North Carolina has been in the top states, but of all U.S. cotton-producing states, the only two that had acreage reductions this year were North Carolina and South Carolina. All Mid-South states increased acreage.”
This is the third or fourth year the state’s cotton growers have had to contend with cool, wet spring weather, Dodds notes. “It seems this has become more the norm than the exception. Then the weather turned dry, and some parts of the state went five weeks with no rain. It’s always amazing how quickly moisture can run out.”
Wide variations in emergence
In many areas, he says, the moisture differential resulted in wide variations in emergence. “It wasn’t unusual to see three-leaf or four-leaf cotton next to cotyledon cotton in the same row in the same field. We got a lot of phone calls about this, particularly with regard to thrips — questions about how to manage thrips when some of the cotton was getting past the thrips stage, while other cotton was still in the cotyledon stage.”
Rainfall has been more extensive than normal in the northern part of the state, he says, and crop development has been moving along better. “Conversely, on our campus plots at MSU, going into July, we had seen hardly a drop of rain.”
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Some growers replanted cotton, Dodds says. “Herbicide injury has seemed worse this year, and we saw a fair amount of sandblasting in the Clarksdale area due to strong winds toward the end of May; some of that cotton was replanted into June.
“As things stand now, we can’t control pigweeds with glyphosate and other products. We’re relying heavily on Liberty, and in my opinion, it’s just a matter of time before resistance starts showing up with that product. Additionally, we’ve confirmed resistance to PPO materials in the upper Delta and in other cotton areas.
“If PPO resistance spreads as quickly as glyphosate resistance, that pretty much leaves Liberty, in the absence of dicamba or 2,4-D. If we start seeing issues with Liberty, that will put us behind the 8-ball in terms of weed control — not just in cotton, but also in soybeans. While cotton is only a 9 million to 10 million acre potential resistance problem, if you add in soybeans it becomes a potential 100 million acre problem. We need to do everything we can to protect these products as long as we can.”