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Sticky cotton changing tenet

Integrated pest management's foundational principle is treat for pests “just in time” to prevent damage.

However, IPM's tenet is being tossed out the window in the San Joaquin Valley where many cotton growers are telling their pest control advisers that when it comes to controlling silverleaf whitefly, make it “just in case.”

Growers who two years ago refused to spend money late season to control whitefly spent thousands in 2003 to control the pest whose honeydew can gum up textile mills as if Elmer's Glue was mixed with the cotton.

Sticky cotton from the 2001 SJV crop sent shock waves through textile mills worldwide and overwhelmed the SJV cotton industry, threatening the long-standing reputation of SJV cotton as among the finest in the world.

The primary culprit is the silverleaf whitefly (SLWF), although aphids can also cause stickiness.

SLWF is a baffling bug. The tiny critter does not impact cotton yields, but honeydew from a whitefly horde can ruin open bolls at harvesttime.

The tiny terror is what brought leading pest control advisers, chemical company representatives and University of California entomologist together recently at the Kearney Agricultural Center for a round table discussion on how to economically control the pest without breaking the budget or building up resistance to some pesticide classes with pesticide overuse.

UC IPM advisor Pete Goodell called the gathering because demands for sticky free lint requires pest managers to use the same tactics as high value vegetables where growers spend hundreds of dollars per acre to protect the appearance of the crop.

To date California PCAs and UC entomologist have utilized information developed in Arizona to monitor and treat for SLWF. However, it has become apparent that the Arizona system does not fit California like a glove.

Different approaches

Arizona has been successful in controlling SLWF in a virtual cotton monoculture. However, with many more whitefly host crops in California, PCAs are discovering large, migrating adult populations in cotton that require different approaches than Arizona.

The Arizona SLWF management plan calls for three stages of treatment beginning with one of the two insect growth regulators, Knack or Applaud followed by a non-pyrethroid and then late season pyrethroids, if necessary.

California PCAs are finding they need to follow IGRs with non-IGRs much earlier than in Arizona because whitefly populations migrate into fields just prior to boll opening.

“Cotton growers are spending a lot of money to protect their open bolls from whiteflies coming from weeds and other crops,” said one PCA.

Timing of late to mid-season whiteflies is a debatable subject. Some PCAs said their clients want zero tolerance for whiteflies when bolls are open. That forces them to recommend sprays when populations are just building rather than wait until they are considered economically damaging. By then it may be difficult to control the pest to a zero sticky tolerance, and PCAs will not risk failure to meet the zero tolerance grower mandate.

Others say that when a small percentage of bolls are open, sprays can be postponed until more bolls are open and maybe get through the season with only one late-season whitefly treatment. If those early bolls are sticky, they can be mixed with clean cotton without any problems in ginning or in the textile mill.

Late cotton this season also made cotton more vulnerable to whitefly honeydew.

“I saw 72-inch tall cotton being irrigated on Sept. 15 on the West Side of the valley last season,” said one chemical company representative. “That tells me there needs to be still more education about the impact of whiteflies on cotton.”

Aphids challenge

While the whitefly is the biggest culprit, aphids can also cause stickiness. They were a challenge in 2003, and it was California's Department of Pesticide Regulation that stepped in to help growers and PCAs bring it under control.

Furadan has received Section 18 emergency exemptions for several years to control late season aphids, but the federal EPA told American cotton growers don't ask for another exemption in 2003 because EPA was convinced that the new chemistry now on the market could control aphids.

“We started hearing late last year that for whatever reason, many of these new products were not working,” said Earl Williams, president of the California Cotton Ginners and Growers Associations.

“The California Department of Pesticide Regulation stepped over EPA to give us an emergency exemption for Furadan in California because it recognized that the grower needed it,” said Williams. This action, he said, was a result of involving DPR in the cotton pest management strategic planning.

The sticking point in the sticky cotton issue is what is considered damaging honeydew levels. When that is determined, discounts can be determined in the classing office and traced back to fields and growing practices.

Most mills have technology to test for stickiness. That same technology is finding its way to growers.

The San Joaquin Valley Quality Cotton Growers Association is testing cotton from member fields this season with a highly sensitive machine to measure stickiness. That was cited as a major step in relating growing practices to clean cotton.

When the controversy exploded in 2001, California Cotton Ginners and Growers Association mounted an aggressive no sticky cotton campaign.

And the problem seemingly went away. There were no mill complaints in 2002, but Williams, said “that does not mean the problem has gone away because we addressed it. We cannot rest on what happened in 2002 because we know it will come back.”

Although the jury is still out on the 2003 crop, indications are that there was more sticky cotton in the valley last season than the year before.

One Indian textile mill has complained about sticky SJV Pima cotton. Williams is investigating whether it was 2003 or an earlier crop and is tracing it back to the gin and grower.

Another gin reported 10 to 12 modules of 2003 cotton too sticky to gin. “The grower stepped up and did the right thing and did not gin the cotton this year,” said Williams. He may hold it for a year before ginning it since there are indications that the honeydew can break down over time. The grower may also feed the cotton to cattle to keep the sticky lint off the market.

“I think most growers, ginners and merchants realize that sticky cotton costs everybody,” said Williams. “People who grow stick cotton are going to be penalized. It is going to cost those growers more to gin their cotton, and they should not get the same price as everyone else. Growers who spend money to control whiteflies and aphids are not going to stand for people who do nothing not being penalized.

There are channels to dispose of sticky cotton without hurting the valley's reputation. What irritated mills in 2001 was sticky cotton showing up in opening rooms without them expecting it.

“There are areas of the world like Sudan which grows sticky cotton. They sell it. Merchants can market it because there are mills who will take discounted sticky cotton,” he said.

“There will probably always be a few who will, for whatever reason, not address the problem of sticky cotton in the field. However, as long as we have safeguards in place to deal with it, that problem has been dealt with,” concluded Williams.


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