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| 9-17-09
After watching helplessly for four years as a fatal disease marched relentlessly across the state, taking out thousands of grove acres, Florida citrus growers may shortly have some new weapons citrus greening.
Low-volume pesticide spraying technology that could be available later this year and an effective repellent to keep disease-carrying insects out of groves, perhaps ready by next year, are two of the early returns on the $16.8 million investment growers made on citrus greening research last year.
Lukasz Stelinski, an entomologist, and Russell Rouseff, a food chemist, have cracked the mystery of what in the guava plant repels the citrus psyllid, a host for the greening bacteria and the primary cause of the disease's transmission. Both work at the University of Florida's Citrus Research and Education Center in Lake Alfred.
The mysterious chemical is dimethyl disulfide (DMDS), found in many plants but in significant quantities in guava, Stelinski said.
Their discovery may lead to the first commercial product against citrus greening available to growers. The Florida Citrus Production Research Advisory Council in August authorized two new contracts aimed at developing a DMDS product that can be applied in groves and repel psyllids for at least three months.
The council and the Florida Department of Citrus have financed the greening research drive along with state and federal money,
Although DMDS effectively repeled psyllids in field tests, the chemical is highly unstable in current forms, Stelinski said. The applications used in the research worked for just three to four weeks.
A cost-effective DMDS application for citrus groves needs to last at least three months, he said.
Stelinski and Rousseff are working with Auburn University and ISCA Technologies of Riverside, Calif., to develop a time-release mechanism to extend DMDS' effectiveness, Stelinski said. That's similar to time-release mechanism used already in medical drugs.
"I think we're on to something, and I'm optimistic we'll have a new tool in the fight against psyllids," Stelinski said. "There's no one thing that's going to control psyllids. I don't think it will be a magic bullet."
Another weapon in the fight was developed by Lake Alfred center entomologist Mike Rogers, whose research shows low-volume aerial spraying with the pesticide Malathion 5 effectively knocks down psyllid populations.
A low-volume aerial spray program could address two vexing issues in the fight against greening: "Bad neighbor" growers who don't take the recommended efforts on psyllid control and abandoned groves.
Both result in safe havens for large psyllid populations that eventually spread to neighboring groves. Growers who are taking the costly recommended steps against psyllids have complained that fight is compromised by bad neighbors and abandoned groves.
Because a low-volume spray program can cover tens of thousands of grove acres in a matter of days, it could be employed on abandoned groves at little additional expense to participating growers, Rogers said. The lower cost also could entice greater participation from bad neighbors in the psyllid eradication effort.
"We can probably get more people to join in at a fraction of the cost" of ground sprays, he said. "A lot of growers around that (abandoned) grove may be willing to pick up the cost."
Aerial Malathion sprays cost about $6 to $8 per acre, roughly a third the cost of other aerial and ground pesticide applications, said Doug Bournique, executive director of the Indian River Citrus League. The Rogers team used Indian River groves in its research showing the low-volume sprays can effectively kill psyllids.
"It's the best bullet we have in the revolver to fight this disease," Bournique said.
Aerial Malathion is cheaper because it works with just one gallon per acre of the water-pesticide mixture, Rogers said. Other EPA-approved aerial pesticide sprays need 10 gallons or more per acre.
That means an airplane carrying 500 gallons of the pesticide mixture can cover just 50 acres per flight, requiring weeks to cover large areas, he said. That same plane can apply aerial Malathion over 500 acres in a single flight.
The lower amounts of pesticide makes the technology environmentally friendly.
The Indian River League is developing an area-wide program for this fall on groves in Indian River and St. Lucie counties west of Interstate 95, Bournique said. Growers owning more than 80 percent of groves in that area already have agreed to participate, and Bournique expects virtually 100 percent cooperation by the first spraying in the fall.
Read the original article from The Ledger.