When growers in the Gulf Citrus Health Management Area in southwest Florida first started coordinating spraying efforts to combat the Asian citrus psyllid, they weren’t sure what the results would be.
But now, after three seasons, they’re hearing some good news.
“Compared to other areas of the state that are behind us in these organized sprays, we have a relatively low incidence of these vectors,” says Mark Colbert, general manager for A. Duda & Sons Inc. in Oviedo.
CHMAs—or citrus health management areas—were recommended in 2010 by a group of scientists from the National Academy of Sciences. The Florida Department of Citrus had commissioned the report to help the industry survive psyllids and avoid citrus greening disease—also known as huanglongbing or HLB—that they spread.
The purpose of CHMAs is to coordinate the timing of psyllid sprays to enhance control beyond what one or a few growers can achieve on their own, says Michael Rogers, citrus Extension entomologist at the University of Florida’s Institute of Food and Agricultural Sciences Citrus Research and Education Center at Lake Alfred.
If one grower sprays and his or her neighbors don’t, the psyllid can simply migrate in from the untreated areas and reinfest the treated grove.
The National Academy of Sciences report also suggests that growers each time all use the same pesticide mode of action for their coordinated sprays to thwart pesticide resistance. Then they all rotate to a different mode of action.
The popularity of CHMAs has risen dramatically, Rogers says. As of early September, 34 CHMAs had been formed throughout the state covering 426,000 acres of commercial citrus groves.
The concept of CHMAs isn’t new. Some growers have been coordinating psyllid control sprays for several years.
Responding to grower requests, University of Florida’s IFAS and the Florida Department of Agriculture and Consumer Services established a formal statewide CHMA program in 2010.
The Gulf CHMA was the first and largest CHMA, covering 100,000 acres, says Phil Stansly, IFAS entomology professor based at the Southwest Florida Research and Education Center in Immokalee.
The Gulf CHMA is different from others in that it’s made up mostly of large-scale growers, Stansly says. It’s also less regimented. “We don’t get into the micromanagement part of it,” Stansly says. “It’s a little easier to reach a consensus that way.”
The CHMA focuses on dormant spraying, when trees aren’t growing and the psyllid population is unable to reproduce.
“Dormant sprays are quite inexpensive,” he says, and give growers “more bang for their buck.”
Growers are “ecstatic,” Stansly says about the resulting in “a general decrease in the [psyllid] population.”
IFAS Extension agent Chris Oswalt has seen mixed results among the 10 CHMAs in Polk and Hillsboro counties.
“Some of the CHMAs are more active than others,” he says.
Generally, once a CHMA is established, participation increases over time as the word spreads and more growers decide to get involved.
But getting a group of growers to agree on the details of a spray can be a challenge. “It’s difficult to coordinate,” Oswalt says, because growers have varied production schedules and different activities in their groves at different times.
Oswalt is hopeful that, even if just a portion of an area is sprayed, other growers will see the benefits and join the program.
CHMAs haven’t really caught on yet among growers in the area served by the St. Lucie County Extension Office in Fort Pierce, says Tim Gaver, University of Florida citrus Extension agent.
“They just haven’t lent their blessings to the CHMA process,” he says.
That’s because some growers say they think CHMAs cause conflict with their fresh fruit harvesting operations, Gaver says.
“It messes up the planning if you get an order and need to pick 10,000 boxes of fruit, and you’ve sprayed everything and you can’t harvest,” he says.
Growers who produce citrus for processing have a more flexible spraying schedule, Gaver says.
Growers in a few areas have been conducting the CHMA function for a couple years, and Gaver hopes to have a CHMA started soon.
At the Indian River Citrus League in Vero Beach, Doug Bournique, executive vice president, attributes the lack of interest to the fact that about 80 percent of the area’s citrus goes to export.
“It’s a different world here than it is anywhere else,” he says.
Growers may perceive that export buyers fear the spraying would further add to already unrealistic maximum residue levels set by some European countries, Rogers says.
Nonetheless, “We still have growers who are working together when they can to knock the population of the psyllid down,” Bournique says, adding that the league passes along information about CHMAs to its members.
Webpage in the works
Eventually, a webpage will be created that includes a map with the location of each commercial citrus grove within each CHMA, a schedule of planned coordinated psyllid sprays, contact information for grower representatives and a news section to remind growers of upcoming CHMA planning meetings and planned sprays, Rogers says.
The U.S. Department of Agriculture and Florida’s Division of Plant Industry are counting psyllids in 6,000 blocks of citrus in three-week cycles. And Greg Carlton, chief of the Florida Department of Agriculture and Consumer Services Bureau of Pest Eradication and Control, has the responsibility for posting psyllid counts on the Web.
At the end of each cycle, he’ll place psyllid counts on an IFAS-hosted website—www.flchma.org—with a map of various CHMAs indicating whether psyllid populations are increasing or decreasing.
“The growers will take that information and use it to make decisions on when they’re going to spray,” Carlton says.
Counts will help
Colbert of A. Duda & Sons is glad to see that follow-up count.
“Now I’ll be able to look at a map on a website and see where populations of psyllids are getting bigger,” he says. “We might be able to cut out a number of sprays based on the evidence that we have. With the cost of input materials, nobody wants to spray repeatedly unless it’s absolutely necessary.”
The cost of spraying is $200 to $300 per acre per year or more, but it must be done.
“If you don’t control psyllids, it’s almost impossible to stay in business,” Colbert says.
Growers’ biggest objections to the program are cost and inconvenience, says Peter McClure, agricultural research manager for Evans Properties in Vero Beach.
If a grower wants to harvest when researchers say it’s the best time to spray, it’s a problem, he says. But growers generally have been cooperative.
“You have to work out the scheduling and the logistics with your neighbors,” McClure says.
The more growers who participate in a CHMA, the better off they’ll be, he says.
“Ultimately, the less you’ll have to spray and the cheaper it costs to control [the psyllids],” McClure says.
Growers interested in establishing a CHMA should contact their local IFAS citrus Extension agent, who will help arrange planning meetings and will be available to help develop a plan of action, Rogers says.