Recent cancellation announcements for products that have been mainstays for pest control along with increasingly large numbers of weed species and other pests developing resistance to once highly effective products emphasizes the need to practice product stewardship.
Cotton farmers have to be smart about using available tools to manage insect, weed and disease pests and to ensure that effective tools remain available into the future, say university pest management specialists.
University of Georgia scientists discussed potential for new products to help farmers manage weeds, insects and diseases and offered suggestions on keeping current chemistries effective during a Crop Consultants’ Conference, a segment of the annual Beltwide Cotton Conferences held recently in Atlanta.
R.C. Kemerait said consultants need to help growers “make the best decisions” on using seed treatments for nematode and disease control. “Ten years ago, seed treatments were primarily fungicides,” Kemerait said. “Now, we are more aggressive with seed treatments and have new chemistries that expand the pest control spectrum.”
He said in-furrow pesticides may be more effective but growers “appreciate the convenience of seed treatments.”
Also, the most popular in-furrow product, Temik, will be off the market in a few years. “Seed treatments will sustain the stand,” he said. “There is nothing like Temik and I don’t think we will have anything like it again.”
Losing that product has generated interest in controlling nematodes, he said. “So, how do we use existing technology to get necessary control of nematodes?”
He said Telone II is one possibility but is expensive. “Risk management zones may be one practical approach.” Nematodes are distributed according to soil type. Southern root-knot nematodes tend to populate sandier soils, for instance.
Kemerait said identifying soil types and targeting those areas with treatments improve efficacy and economy of Telone applications.
He also recommended choosing cotton varieties with nematode tolerance when possible. He also noted three fungicides labeled for cotton—Topsin-M, Headline and Quadris.
“Don’t take nematodes or diseases for granted,” Kemerait said. “We do have tools to control them.”
Few new products
Phillip Roberts said farmers can’t expect a lot of new products for insect control so product stewardship remains a critical commitment.
Cotton has done its share over the past 25 years in preserving insecticides and protecting the environment, he said.
“In 1986, Georgia cotton farmers averaged more than 15 applications per year. That was the year prior to the boll weevil eradication program. From 1992 through 1995, we averaged four or five sprays a year. We had eliminated the boll weevil and saved a lot of spray applications.”
The boll weevil program also allowed farmers to use integrated pest management systems.
“In the early 1990s we targeted worm control and sprayed four or five times with pyrethroid insecticides. When Bt cotton came on in 1996, we cut down to two or three applications per year. Now, we’ve seen a shift in insect populations.”
Roberts said IPM has become more widely used. “IPM means using all the control tactics available so economic losses and harmful environmental side effects are minimized,” he said. “We put a premium on scouting and our objective is to preserve an economic yield.
“We have great tools and our tools will get better, but we will still have yield-limiting pests. We continue to need innovation for control.”
He said a few new products are coming on line, including Belt, Belay and Coragen. Pre-mixes and co-packs are also important tools, he said. “Be sure both active ingredients are included in premixes,” he said.
Resistance prevention is also important, Roberts said. “Cotton has a complex of pests.” And even similar pests may require a different control program. “Brown or green stink bugs, for instance, need different controls. Also, corn earworm or fall armyworm may be in the mix. Treating for one pest also may affect the population of another pest.”
He said cultural practices such as tillage, planting dates, use of at-planting insecticides, control thresholds and susceptibility affect management strategies.
“And even with Bt cotton, we still need IPM. New technology is coming with WideStrike Advanced, BGIII, and TwinLink. We’re also concerned with loss of Temik and methyl parathion.
“Resistance is a concern and we have to ask: Are we using IPM to the fullest extent possible?”
Stanley Culpepper said new chemistry for weed control will be a welcome addition, especially when developing tactics to combat glyphosate resistant weed species. “Warrant fits a similar application window as Dual Magnum for Palmer amaranth,” he said. “That gives us another tool.”
He said GlyTol, WideStrike and Liberty Link cotton are also important players to provide “broad spectrum weed control. We have to understand tolerance,” he said.
“Roundup and Ignite offer more options to control weeds,” Culpepper said. “One fills in gaps where the other is weak. But we will still have weak areas.”
He said farmers should develop a “systems approach for resistant Palmer amaranth, using several chemistries and other practices.
“Using GlyTol or Liberty Link requires exact timing,” he said, “for effective control. If you can’t be timely, technology will not work for you.” He said water volume, nozzle types and time of day all make a difference. “Do not apply Ignite within an hour of sunrise or sunset,” Culpepper said. “Also, with Ignite, you must kill the weed with the first application.”
He said 2, 4-D resistant cotton will provide new opportunities but with challenges to manage drift as well. “It will be a tool for managing giant ragweed, horseweed, Palmer amaranth and others. But neither 2, 4-D nor Clarity are effective at controlling large Palmer amaranth. Farmers have to be smart,” he said. “We need to maintain currently used herbicides and be aware of potential for off-target movement of 2, 4-D and Dicamba. And don’t abuse Ignite.”