NEW ORLEANS (AP) — State and federal workers are checking trees in the heart of Louisiana's citrus country because trees in nearby New Orleans were infected with citrus canker, a dangerous infection that had been found only in Florida since 1945.
The bacterial infection damages all kinds of citrus from kumquats to grapefruit, causing a gradual decline until the tree stops producing any fruit. Before that happens, infected leaves and fruit may fall early, said Raghuwinder (rahg-oo-WIN-der) "Raj" Singh, a plant pathologist at the LSU Agricultural Center.
Alan Vaughn at the AgCenter's Citrus Research Station in Belle Chasse said he's had calls from people worried that their trees might have the disease — but it hasn't been found so far in Plaquemines Parish, where half of Louisiana's 600 acres of citrus orchards are located. The rest are scattered across 16 parishes from Beauregard to St. Bernard.
"I'm telling them, get it tested. Don't be pulling the tree up or anything now," because they may be looking at a treatable fungus called citrus scab that looks ugly but doesn't hurt the fruit, he said.
The bacteria cause raised brown spots on leaves, fruit and twigs. On leaves and fruit, the spots are surrounded by an oily, water-soaked area and a yellow ring around that.
Citrus canker is one of two diseases that have quarantined all of Florida's citrus: plants, leaves and twigs cannot leave the state unless they're certified free of the diseases. Fruit — including fruit grown in home yards — must be treated at a commercial packing house and federally certified before crossing the state line.
The bacteria causing canker can get into trees either through the pores through which gases go in and out of leaves or through injuries such as those caused by insects. It is spread by wind-driven rain, by contaminated tools and equipment, or by moving infected fruit, plants or parts of plants.
It's thought to have originated in southeast Asia, and has been found three times in Florida — in 1910, 1986, and 1995. The first time, it spread as far as the Gulf states and South Carolina. It was eradicated in the Gulf states in 1943 and nationwide in 1945, according to the U.S. Department of Agriculture. After the 1986 discovery it was declared eradicated in 1994 but found again a year later. In 2005, the USDA said eradication was no longer possible in Florida.
A USDA employee in New Orleans who had worked with two other citrus diseases noticed an infected sweet orange tree while jogging after work in City Park around June 10, said Bill Spitzer, state plant health director for the U.S. Department of Agriculture.
"She went by the tree and thought that it looked a bit different from citrus she had seen in her normal work. She came back later and took a sample for analysis," he said.
He was notified June 24 that the tree did indeed have canker, caused by the bacteria Xanthomonas axonopodis (zan-thuh-MOH-nuhs AX-on-uh-POH-dis).
That tree and two nearby, all within 10 feet of each other, proved to be infected. All three were quickly removed from City Park for incineration, said Veronica Mosgrove, spokeswoman for the Louisiana Department of Agriculture and Forestry.
Since the lab test proved positive, Spitzer said, USDA and state employees have checked City Park's trees and 10 to 15 locations within a mile of the park — "a real quick spot check to see whether it's prevalent or hard to find. It's hard to find," he said. "That indicates it's real light in there."
Inspectors did find one infected yard tree, he said.
The trees at City Park were planted together about three years ago, Mosgrove said.
Singh estimated they were infected within the past year because older growth didn't show any canker scars.
"I can tell you they were not infected when they were planted," he said.
Copyright 2013 The Associated Press.