Cotton harvester working Central California Acala crop

California's reputation for clean, quality cotton is vital to an industry with diminishing cotton acres.

California cotton seeks upper hand on whitefly

Whitefly populations have been seen earlier in recent years. IPM control measures can help, but chemical treatments are still necessary. California cotton acreage is significantly down this year, due to drought and price competition from other crops.    

California’s reputation for clean, quality cotton is a concern this year due to limited acreage and sticky cotton reared its head last year.

While pink bollworm survey numbers will not confirm it until July, Roger Isom, president of the California Cotton Ginners and Growers Associations, is relatively confident in early acreage estimates of 188,000 for the statewide crop. Isom expects 130,000 acres of Pima and 58,000 acres of Upland cotton.

This is about half of last year’s total California crop. Drought is the major factor in declining acreage numbers this year.

Industry leaders are working to get ahead of the sticky cotton issue this year through three meetings hosted by the Fresno-based California Cotton Ginners and Growers Associations. The meetings were held in Tulare, Shafter and Five Points in mid-June.

Isom says the industry intends to host outreach meetings at various gins in the coming weeks to address the issue.

According to Pete Goodell, IPM expert with the University of California Cooperative Extension, the issue is one of sugar left behind by feeding white flies. This is why control of the pests is vitally important for the industry. Early July is not too soon to begin surveying cotton fields for whitefly populations.

“What you end up with is a fluffy cotton boll covered in sugars that collects everything,” Goodell said.

“Think of it as cotton candy at the carnival,” he told growers and pest control advisers (PCAs).

“Here’s the pun of the day,” Goodell joked, “Once a region develops a reputation for sticky cotton it really sticks with you.”

Quality cotton is clean cotton

Cotton gins need dry, fluffy cotton to easily roll through the ginning equipment. Some growers and ginners agree that there were issues with last year’s California cotton crop.

“Insect sugars will immediately shut down a mill,” Goodell said. "One or two bales can cause a problem and shut down a mill for a week. This is why people never forget who gave them the sticky bales.”

While sticky cotton can be particularly troublesome for cotton gins, textile mills can blackball entire growing regions over the issue, Goodell said.

The silverleaf whitefly is the major culprit in sticky cotton, according to Goodell. Populations usually peak in September when bolls are open. It has other seasonal hosts, including alfalfa, citrus, weeds, tomatoes, and melons, which makes control more difficult.

While cultural whiterfly controls exist, Goodell recommends chemical control as well since no single IPM enemy has been identified to manage whitefly populations. Pyrethroids are a common tool because they are labeled for multiple crops. Just be sure to check the labels, he says.

One factor partly responsible for the increased whitefly populations is the California drought. Whitefly populations are present in many areas of the San Joaquin Valley which are normally well managed, but last year the population was more widely distributed and a little more difficult to control. The whitefly was seen throughout the cotton growing region.

Controlling nymph populations is critical to the issue because the pest produces most of the honeydew that causes sticky cotton, and nymphs do not move, said Larry Godfrey, an extension entomologist with the University of California.

Whitefly populations developed earlier in 2013 than expected, Godfrey says, with pests seen in areas not commonly found. Those populations exploded within a relatively short time frame as well.

According to Godfrey, some of his research plots saw exponential growth in whitefly populations in as few as 15 days.

Recommendations

Sampling is the key, Godfrey says. Growers and PCAs should walk cotton fields and sample 30 leaves in different locations; looking at the fifth leaf from the top. These recommendations are based on the Arizona system and should work well for California.

Look for the presence of pests between the veins and use a magnifying lens for the nymphs. Count only the large third or fourth instars.

When sampling leaves, immediately count the adults on the underside of leaves since the bugs will quickly fly away. Then count the nymphs, Godfrey says.

Goodell recommends checking fields twice a week. Whiteflies tend to build first on the edge of the field.

Goodell recommends selective whitefly insecticides during the earliest period of invasion in order to preserve beneficial insects.

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Goodell invites growers and PCAs to contact him at the Kearney Ag Station in Parlier, Calif. with questions and input at (559) 646-6515.

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