Most cotton growers probably don't give much thought to the bathroom habits of insects. But the sugary, sticky excretions from millions of whiteflies and aphids can cause stickiness of cotton lint and can cost growers 3 cents to 5 cents a pound in discounts.
Further, the stickiness caused by this “honeydew” can significantly slow the ginning process and gum up machinery at textile mills, causing yarn breaks, spinning slowdowns/stoppages, and imperfections in fabrics.
Worse still, said specialists at the recent Western Farm Press-sponsored fifth annual Pima Cotton Production Summit at Visalia, Calif., sticky lint can cause damage to a cotton producing area's reputation that can take years to overcome.
“Arizona had sticky cotton problems in the late ‘80s and early ‘90s,” said John Pucheu, Tranquillity, Calif., Producer, “and it almost killed their industry. This cotton sells, on average, for five cents a pound less. Once an area gets a reputation for sticky cotton, it's awfully hard to overcome.
“You may think, ‘Well, we're growing a lot of our cotton for the loan and so we'll just market the unaffected cotton and put the sticky stuff in the loan.’ But we're kidding ourselves if we think the government is going to accept this cotton year after year and build large inventories of sticky cotton.”
In some cases last year, cotton was “so sticky it would barely go through the gins,” Pucheu said. “Where 15 bales per hour would be normal, they were able to run only two to three bales.
“Fortunately, there wasn't too much of it, but it got into the marketing chain and customers complained. Some began substituting Egyptian cotton. We stand to lose a lot of customers if this continues.”
Should be concerned
Although sticky cotton has been a problem to some extent in Acala varieties for more than 15 years, said Pete Goodell, University of California IPM entomology specialist, “It's something every Pima grower should be concerned about.”
Why stickiness was a problem for many California growers last year, as opposed to other years, “I'm not quite sure,” he said.
Possible causes: “The whiteflies arrived early, aphids built up later than usual, the crop was late in some cases, and there was no late rainfall to help rinse the excretions from the lint.
“Southern Kern County fields were treated almost a month earlier than usual — in June rather than July — following an exceptionally warm May, with 10-plus days of temperatures greater than 90 degrees. And all this was preceded by a mild winter that allowed a lot of insect survival.”
The hot temperatures, Goodell said, resulted in a shortening of the interval of whitefly generations, with larger populations.
Also, he said, because of the lateness of the crop, there probably was a period between the time the PCAs left the fields and the crop was ready for defoliation that the cotton wasn't looked at for a couple of weeks. This may have allowed the whitefly populations to build to levels that should have been treated.
In a subsequent question-and-answer session, one grower noted that, “Bankers and lenders won't finance end-of-season treatments when operating budgets have run out. Over the past five years, this has been a significant problem, and unless we can get these people in the loop, we can't make these applications.”
Hold money back
Peter Ellsworth, University of Arizona IPM specialist, Department of Entomology at the Maricopa Ag Center, said, “We've targeted some educational programs to bankers to help them understand what's at risk, but you may have to look at where you're spending your money early season and hold some back for late season treatments.
“Some of the biggest problems we have are PCAs and growers opting to treat for whiteflies too early in the season and running out of money for late season treatments. We're suggesting that they instead use an insect growth regulator (IGR) early and then an insecticide for late season control.”
Even after 10 to 12 years of hard knocks from the whitefly in Arizona, “there still is a major problem of grower complacency,” Ellsworth said. Unfortunately, in too many cases, “sticky cotton isn't that obvious in the field — you can't judge the seriousness of the problem by sooty bolls.
“It's an invisible stranger; we don't have a really good grasp of what it should look like in the field.”
But, it is “a horrendous problem that not only contaminates the crop — it also contaminates markets. After Arizona's 1992 stickiness problem, prices were reduced 3 cents a pound on average. When this occurs, you're not fighting just for this year's price, you're going to be fighting for at least five years. In the late 1980s, we enjoyed a premium over New York futures. The stickiness has been a significant factor in major price penalties.”
Nymphs real problem
Nymphs of the insects are the real culprits, Ellsworth said. “They're nothing but eating machines, and their excretions can completely cover plant surfaces. These huge populations can also contribute to water stress from which the plants can't recover. If just one farm has a sticky cotton problem, it can affect the entire community and put everyone's crop at risk.”
Fortunately, he noted, “We do have the tools and techniques to effectively and aggressively manage these pests in the majority of cases.” A three-pronged program of sampling, effective chemical use (both IGRs and insecticides), and avoidance can greatly reduce the problem.
“We have some quite extraordinary chemistry available, including Knack, Applaud, and Admire, with others coming along. The toolbox is full and there is plenty of information available for effective use.”
As a result, Ellsworth said, “We've seen control costs go ‘way down, to the point that some growers thought we'd vanquished the pests. In 1996, we were averaging four sprays per season, now only one, with materials that have much lower toxicity. Growers have saved $69 million in treatment costs since '96.”
But sticky cotton occurrences in 2001 served as “a wakeup call, emphasizing that we can't be complacent about this problem.”
For effective avoidance and control, Ellsworth said, it's important that there be communication between growers area-wide, including cross-commodity cooperation.
The Pima Production Summit was sponsored by the University of California, the Supima Association of America, the California Cotton Ginners and Growers Associations, Western Farm Press, and the University of California Cooperative Extension Service.