Report details steps for battling Florida citrus greening

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 today 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 Andrew Meadows, spokesman for the industry trade group, Florida Citrus Mutual.

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 federal National Research Council to outline steps to overcome the threat of greening, first found in the state in 2005.

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 over the past three years, the majority on citrus greening, Meadows said.

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

The disease is spread by the Asian citrus psyllid, which on its own 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, though 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 to control the insect: Insecticides are the only method 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.

Ladybugs, beetles, lacewings and other insects prey on psyllids but don't devour enough to blunt the population.

Promote research to detect the disease earlier: Spotting symptoms is the only way to detect greening, and it can take months for symptoms to be visible on an infected tree, the report said. During that time, the infected tree can spread the disease through the grove.

Researchers should try to develop a test to detect the disease faster to reduce the spread of the disease.

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: Grove owners could plant types of citrus that grow and reach commercial maturity 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 and soon spread through South Florida. It reached the Tampa Bay area in 2007 and 2008.

The psyllid has also been found in Arizona and California, though groves in those states show no sign of the disease. The disease has also shown up in other citrus-producing countries.

"It's a global problem," Meadows said.

The disease is an even larger threat to the industry than the canker that growers struggled to eradicate and that cost homeowners thousands of backyard trees before the hurricanes of 2004 and 2005 spread the affliction so widely the state gave up attempts to wipe it out.

Oranges from trees with canker could still be sold for juice, Meadows said. Greening kills the tree.