Weed control, quality issues and more efficient means of production all are on the minds of Southeastern cotton producers as they enter the 2001 growing season. North Carolina State University Extension cotton specialist Keith Edmisten discussed each of these topics at the recent Southeast Cotton Conference in Raleigh.
Referring to research conducted by Alan York of North Carolina State, Edmisten says the herbicide Harvade, when used as a directed spray, must be applied precisely. “It is a fairly hot herbicide, and it provides a very limited amount of residual control. The weed spectrum is limited, based on our experience at this point,” he says.
Harvade's biggest strength, notes Edmisten, is when it's used against morningglory. “There's some concern about antagonism, especially with Roundup and grasses,” he adds.
Harvade and Roundup and Harvade and Caparol have been added to the N.C. State recommendations for 2001, but only as a directed spray in situations where morningglory, sicklepod and pigweed are a problem, says the agronomist.
Edmisten also discussed cotton injury with Roundup and Staple mixtures. Some growers reported injury from this mixture during the 2000 growing season, he says.
“We looked at Staple alone, Roundup alone, Staple plus Roundup and the pre-mix and Staple and Roundup. There is more injury from the pre-mix or Staple plus Roundup when compared with Staple alone, but it decreases over time. There essentially was no difference in lint yields.
“The take-home message here is that you do have potential for more injury from this mixture. You may want to avoid situations that would exacerbate Staple injury, such as cool weather conditions. You also might want to avoid this type of injury if you have extremely late-planted cotton and you want to avoid delaying maturity. Otherwise, we feel pretty comfortable with this mixture,” says Edmisten.
Growers also will have a new form of Touchdown to add to their weed control arsenal this year, he says. The new formulation of the herbicide contains glyphosate with IQ technology, and it is not the same as the old Touchdown 5AS. It can be applied in-crop to Roundup Ready corn, cotton and soybeans, he says.
Neither Touchdown IQ or Roundup Ultra had any effect in terms of yield or injury in university-conducted trials, says Edmisten. When two applications were made — one at the one-leaf stage and one at the four-leaf stage — yields were within 20 pounds of each other.
Edmisten also talked about the proper application of glyphosate or Roundup. “We need to consider timeliness when applying Roundup. It needs to be applied before weeds become too big to kill and before they compete with the crop. Also, there are concerns about applications after the four-leaf stage due to boll shed.”
The timing of glyphosate applications can have an effect on cotton yields, he says. “We see a good boost in yields when we apply at the one-leaf stage as opposed to waiting until the three- to four-leaf stage. Cotton shouldn't have to compete with weeds.”
Growers also have had questions concerning the uptake of Roundup through the stems or through the leaves, he continues. “We've seen no problems with precision applications in yield trials. When I say precision application, I mean putting it on the cotyledonary nodes and down. There's lab data from North Carolina, Georgia and Mississippi that indicates that maybe we get more uptake through the stems than through the leaves.
“So, what about a sloppy directed application? In other words, applying above the cotyledonary nodes, which, in some cases, will be necessary to cover the weeds. Georgia has one of the few trials in which cotton was not able to compensate for fruit loss due to a sloppy Roundup application.”
When making a directed application at the four-leaf stage, is it advisable to use Roundup or conventional chemistry? asks Edmisten. Roundup would be preferred for grasses, especially if grasses have become very large, he says.
“MSMA doesn't do as good a job as Roundup when annual grasses become too large. Otherwise, conventional chemistry is preferred for better morningglory control, residual control, resistance management strategy and to avoid the weed shifts that we might see in a Roundup-only system. Conventional chemistry also reduces the risk of boll shed.”
Quality is another concern of growers as they enter the 2001 production season, says Edmisten. “In the past, we've seen a high mic year with low staple. But they've never separated out like they have in the past few years, and that's alarming. Of course, last year was a low mic year because of the rain and cloudy weather.
“People want to blame the quality problems on Roundup, cotton variety or the environment.
“But the problem is becoming worse, and it's probably the result of some combination of all of these factors. And it's certainly not a problem just in North Carolina. It's been a problem throughout the Cotton Belt, and the textile mills are very concerned.”
“The increasing costs of producing cotton have led to an increased interest in skip-row cotton in the Southeast. Based on our trials, we feel fairly comfortable with a skip of 14 to 16 inches. Because of stalk size, I'd be very careful about going much over 16 inches. We've looked at skips from eight to 16 inches, and we've seen little difference in terms of yield when compared to solid cotton.”
Variety selection and avoiding stress are very important in improving staple and strength, notes Edmisten. “Staple length is developed in the first half of the boll's life. During that period, we need to avoid stress. Variety selection also is important in improving strength. Adequate potassium also will improve strength and staple, but we don't need to go overboard with K applications.”
Edmisten encourages producers to look not only at yields but also at quality characteristics when selecting cotton varieties. “We have a serious problem with staple, mic and strength. Don't make a variety decision based on yield alone.”
The increasing costs of producing cotton have led to an increased interest in skip-row cotton in the Southeast, he says. “Based on our trials, we feel fairly comfortable with a skip of 14 to 16 inches. Because of stalk size, I'd be very careful about going much over 16 inches. We've looked at skips from eight to 16 inches, and we've seen little difference in terms of yield when compared to solid cotton.”