Home > News & Media > Ph.D.s put heads together to combat citrus greening

Ph.D.s put heads together to combat citrus greening

Palm Beach Post – April 25, 2008

By SUSAN SALISBURY
Palm Beach Post Staff Writer

FORT PIERCE — The sex life of the Asian citrus psyllid provided one of the few light moments during a conference about the disease those insects spread: Citrus greening.

A 1-minute video showing a male and female psyllid finding each other among the citrus leaves, “mooing” as they got acquainted, also demonstrated one of the few options Florida’s citrus industry has as it tries to survive while enduring the onslaught of the bacterial disease.

Greening has spread to 30 citrus-producing counties since first being detected three years ago and continues to be found in commercial groves. Citrus trees infected by the disease produce misshapen, bitter-tasting, unmarketable fruit.

Florida’s orange and grapefruit growers are putting their faith into scientific research to pull them out of this problem.

More than 80 Ph.D.-level scientists from the United States, Spain, Brazil, Australia and South Africa gathered this week at the U.S. Horticultural Research Lab in Fort Pierce to share the latest findings about the disease.

“This is the most difficult problem I have ever seen,” said Gail Wisler, a national program leader in horticulture at the U.S. Department of Agriculture. “Everything that works well with other diseases does not work well.”

On Thursday, separate recommendations reached during closed-door sessions Wednesday by a “swat team” of 12 USDA Agricultural Research Service scientists, as well as a group of 23 scientists from The National Academies.

Over the next two years, growers will provide a research budget of $20 million to tackle greening, up from $7.5 million for 2007-08 that would have been spent for marketing. The industry also is seeking help from the state and federal governments.

“Time is of the essence. Trees full of fruit are crashing and burning,” said Peter McClure, chairman of the Citrus Production Research Advisory Council and a vice president at Vero Beach-based Evans Properties Inc.

One problem is that the greening bacterium is on a list of restricted agents compiled by the Department of Homeland Security. An effort is being made to remove it from the list, Department of Agriculture officials said, because keeping it there limits research.

“We are surrounded by an ocean of greening,” McClure said. “That’s insane.”

Citrus growers who are attempting to control greening by scouting for infected trees, removing trees and spraying pesticides to kill psyllids are concerned about nearby grove owners who are doing nothing.

“Doing nothing is not an option. The disease will spread,” said Robin Schoen, a program officer for The National Academies.

Schoen said the ultimate solution probably is a citrus tree that has been genetically altered to be insusceptible to the greening bacterium.

“The work has to start soon,” she said.

The U.S. Department of Agriculture’s report zeroed in on a few areas that are not being addressed or where more information is needed.

That included protection for replacement trees such as physical or chemical barriers, development of a greening-resistant psyllid and discovering how trees respond to the disease by examining their RNA.

While no country in the world where greening exists – including Brazil, the world’s largest orange producer – has found a way to get rid of it, the researchers told Florida growers Thursday that they aren’t giving up.

“The good news is that scientific community likes a challenge,” Schoen said.

Growers remain hopeful, said Jerry Newlin, a vice president with Orange-Co. in Arcadia who also serves on a statewide greening task force.

“They gave us an opinion that it is an extremely serious disease, but if we will continue to be diligent about it, they think we can figure out a way to live with it through management techniques,” Newlin said.

Proposed solutions

Here are five possible research paths scientists say should be considered in the fight against citrus greening disease.
• Developing transgenic psyllids that are resistant to the bacteria that cause greening.
• Development of new pesticides.
• Development of insect-repellent plants that could be placed around citrus groves.
• Mating disruption of psyllids through sound.
• Protection of replacement trees through chemical or physical barriers.
U.S. Department of Agriculture, Agricultural Research Service

Click Here to View This Article