Disease could wipe out commercial citrus groves

Florida needs to take immediate action as well as adopt longer-term solutions to combat citrus greening, a pernicious disease that could wipe out the state's commercial groves and backyard citrus trees, a report released Thursday said.

The fatal and incurable disease, spread by an insect native to Asia that first appeared in Florida in 1998, has reached all 34 citrus-producing counties. "It is the most serious citrus disease out there," said Florida Citrus Mutual spokesman Andrew Meadows.

Greening can kill a tree in two years and has the capability to put the state's commercial citrus industry out of business, he said. The disease and killing of infected trees has already reduced juice production.

The Florida Department of Citrus asked the National Research Council to outline steps to overcome the threat of greening.

The report suggests short-term methods and longer-term steps to save the $9.3 billion citrus industry, including research and information campaigns to encourage grove owners to eliminate diseased trees and alert homeowners of the threat to backyard citrus.

The state and growers spent $26 million on disease research during the past three years, the majority on citrus greening, Meadows said.

Some of the money came from a tax the state levies on each box of citrus.

The disease is spread by the Asian citrus psyllid, which weakens trees by feeding on the sap. It also injects a bacterium that causes greening that spreads when other psyllids feed on infected trees. It first appears as yellowing on leaves and spreads to branches. Tree growth slows and the fruit becomes small, irregular and bitter.

Cutting down infected trees is the only way to slow the disease's spread, although grove owners have tried pruning infected branches and increasing fertilizer to affected trees that may keep a tree commercially viable for a time but still diseased.

The report said those control methods do little good.

Among the report's recommendations:

•Find better ways than insecticide to control the insect and develop a test to more quickly detect the disease. Insecticides are the only method known to control the psyllid, but the report said widespread insecticide use has a number of negative potential side effects, including dangers to groundwater, killing beneficial insects and developing mutations of psyllids resistant to the poisons.

In addition, researchers should also study the insect to see whether there are more efficient ways to use insecticides.

•Develop a strain of citrus that resists the disease. No current varieties of citrus resist greening. Researchers could look for genetic transformations of citrus varieties with resistance, ways to activate a tree's own resistance or develop a type of tree that produces an insecticide to kill the psyllids. Meadows said developing the resistant strain of citrus is the long-term solution but would take years.

•Plant varieties of citrus that grow faster so they can harvest fruit and make a profit before greening invades the grove.

Greening was first discovered in Miami-Dade and Broward counties in 2005; it reached the Tampa Bay area in 2007 and 2008.