From near perfect to perfect storm in one season

From just about perfect to the perfect storm is the tale of two Western cotton seasons: 2004 and 2005.

California and Arizona cotton growers and pest control advisers fondly remember the one — ’04 — and cannot wait to forget the other with hopefully a return to normal this season. However, last season was a reality check after a series of relatively benign cotton growing seasons.

Last cotton season was the perfect storm; doomed it seemed from the day it left the San Joaquin Valley dock.

SJV planting weather was lousy for weeks followed by record July heat that stymied the crop followed by early, cool fall that thwarted any chance of a season-saving top crop. It was not much better in the Arizona and Southern California desert cotton growing area. However, any bad weather there paled in comparison to one of the worst whitefly years in probably a decade. The whitefly outbreak was a wake up call not only for Arizona, but California as well.

California had no whitefly problems last season, but the fact Arizona did has raised the guard of California PCAs and producers.

University of Arizona Extension entomology specialist Peter Ellsworth and his IPM counterpart in California, Pete Goodell, said insect losses were higher in 05 than they have been in several years.

Goodell and Ellsworth offered up their analysis of ’05 at the recent Bayer CropScience Cotton Technology Seminar where Ellsworth said he saw whitefly coming last season and put out the warning.


However, in many cases the success Arizona growers have enjoyed for a decade may have been their worst enemy last season because success likely bred some complacency.

“Whitefly numbers were very high last season, and the problems encountered were not totally the growers’ fault. However, there was a lot of complacency in the state last season” and Ellsworth said complacency caught some growers and PCAs short at the end of the season and they “panicked,” spraying heavily to protect open cotton from whitefly honeydew deposition.

The average pesticide bill in Arizona soared to more than $100 per acre, almost three times what it has been reduced to with the successful whitefly management program developed in Arizona after the state’s cotton industry almost went under by the stigma of sticky cotton in the early 1990s.

Arizona cotton growers dug themselves out of a deep hole then working with Ellsworth other UA entomologists and chemical manufacturers in developing a successful control strategy involving unique scouting techniques to monitor whitefly populations; use of Admire systemic pesticide in vegetables and melons; judicious use of two new insect growth regulators and rapid adoption of Bt cotton to reduce overall pesticide sprays and preserve whitefly predators. It was all part of an area wide approach to controlling whitefly that has been a benchmark for controlling the multi-host whitefly.

Despite a solid control program for a decade, whitefly reared its ugly head once again in ’05. However, Ellsworth said it was not as bad as the year prior to development of the successful control strategy and hopefully ’05 Arizona cotton will “go under the radar” and escape the sticky cotton stigma.

Whiteflies overwinter

Ellsworth suspected the warm, wet winter before spring planting produced a big overwintering population of whiteflies. A trip to the Yaqui Valley of Mexico about 300 miles south of the Arizona-Mexico border early in the year confirmed Ellsworth worst fears. “What I saw there was the potential for a major problem in Arizona,” he said. There leaves were coated with whitefly and eventually growers there lost 50 percent of their crop to whitefly. That does include losses due to sticky cotton. The loss was so heavy in Mexico because growers there do not have the same improved pest control tools like the insect growth regulators used in American cotton.

Arizona whitefly numbers have been remarkably low for years, noted Ellsworth. Nevertheless, the potential has always been there for an explosion. Ellsworth has documented in his research heavy whitefly populations in plots in past season where there were no whitefly controls measures like Admire.

Cotton growers had grown complacent since for the past several years they have had to foliar treat just one time for whitefly. Ellsworth said some tried to “go cheap” with similar minimal control strategies in ’05 and were caught with late season pressure that sent insecticide spray bills for a “quantum leap.”

Ellsworth said monitoring and following the multi-stage treatment strategy developed in Arizona remains a viable plan for controlling whitefly, especially in early season control strategies.

“It is amazing we have four all-star compounds we can use early against whitefly, all with unique modes of action,” said Ellsworth, citing Knack, Courier, Intruder and the newest whitefly material, Oberon, which Ellsworth said worked well in his pre-registration trials.

Although sticky cotton became a major cause for concern in the San Joaquin Valley several seasons back, it was not an issue in an admittedly bad insect pest year in ’05. California Cotton Ginners and Growers Association teamed with the University California Cooperative Extension to step up and prevent future sticky cotton and it worked. There has not been SJV sticky cotton issue in about four years.

‘Somewhat exempt’

Ellsworth said the San Joaquin Valley “has been somewhat exempt from whitefly problems because of its northern climate. There are not as many generations in the San Joaquin as there are in Arizona.” However, California is not immune to the problem.

Ellsworth warned that just because there is no black, sooty mold on cotton does not mean whitefly has not deposited honeydew. He showed a magnified photograph of a seemingly undamaged bright white cotton boll with honeydew imbedded in the lint. “Just because it is white does not mean it is not sticky” if whitefly numbers become high enough to deposit honeydew into the lint.

SJV’s perfect storm ’05 season fortunately did not include late-season whitefly.

However, there were plenty of insect problems without whitefly.

Goodell said overall insect pest pressure was moderate to severe in the San Joaquin. Thrips were damaging; not surprising considering slow start. When the cotton plant is not growing due to cold weather, thrips cause damage.

Lygus, the valley’s most predominant insect pest, was the worst it had been in 10 to 20 years, “depending on where you were last year,” Goodell noted. “Where lygus were bad, they were really bad.” Spider mites, he added, were “a little more widespread” and have been “getting people’s attention” as a growing problem over the past few seasons. Aphids were widespread in 2005, but “not excessive.”

Despite being one of the most challenging pest years in the past decade, yield losses due to insects were relatively minimal.

Lygus in survey

PCAs and growers told Goodell in an insect loss survey lygus was responsible for about 5 percent of a potential 500 pounds more lint than was harvested. Typically lygus take about 1 percent of the potential yield. Spider mites accounted for about 2 percent of the crop loss.

However, poor weather was given the majority of the blame for dropping Acala/upland average yield to about 1,219 pounds and Pima to 1,274 pounds. Goodell said the potential SJV cotton yield is 1,750 pounds of lint per acre.

“Weather accounted for 16.3 percent of the yield loss,” concluded Goodell.

The perfect storm of 2005 is over, fortunately, and now it is on to 2006. No one wants a repeat, but cool, wet weather arrived on March 1 with two weeks to go to cotton planting season. Perfect storms are rare and growers and PCAs are hoping there will not be a pair of back-to-back rarities.

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