Lethal palm disease found in New Orleans

Symptoms of the fusarium wilt of Canary Island date palm disease that has been found in New Orleans initially shows up on one side of the palm fronds, but over time it will spread throughout the tree canopy. (Photo by Russell Harris. Click on photo for downloadable image.)

News Release Distributed 11/17/10

NEW ORLEANS – LSU AgCenter scientists have discovered fusarium wilt of Canary Island date palm trees in the city for the first time. The disease is previously known to occur in Florida, California and Nevada.

The disease, which interferes with the movement of water by obstructing the water-conducting tissue of the palm tree, was first seen in New Orleans in December 2009, according to Russell Harris, LSU AgCenter horticulture agent.

Fusarium wilt is caused by a fungus that is both soil-borne and seed-borne. It is lethal to the Canary Island date palm, and there is no cure, Harris said.

Trees throughout the city are showing symptoms of the disease, and of the 1,000 or more of this variety in the city, Harris said he’s noticed more than 30 showing symptoms of disease.

“This disease is spread through poor pruning practices, contaminated soil and movement of diseased nursery stock,” Harris said. “My hypothesis is that the disease got here through nursery stock shipped from Florida.”

Infected trees suffer from reduced vigor. The initial, visual symptoms appear on the lower older, mature leaves, then move upward into the canopy as the disease progresses.

“The characteristic symptoms of fusarium wilt include one-sided death of the leaflets,” said Raghuwinder Singh, an LSU AgCenter plant pathologist.

Initially, the leaflets on the other side of the infected frond stay green, but eventually the whole leaf dies and desiccates, he said.

These symptoms shouldn’t be confused with freeze damage, which will affect the entire frond simultaneously, Singh said.

“There are no effective chemical treatments available for this disease,” Singh said. “If the infected palms are left unchecked, these may serve as a disease reservoir, and the fungus can spread to healthy palms.”

In the absence of an effective chemical control, Singh said, good sanitation and cultural practices should be followed to minimize the disease spread from infected to healthy palms.

“Clean pruning tools such as hand saws in a 1-to-3 ratio of pine oil to water solution for five-10 minutes between trees,” Singh said. “This may be practiced for both healthy and infected palms.”

Once a tree has become infected, it may take a few months to years before the first symptoms appear.

“We’re asking homeowners to send us samples of fronds if they suspect they have the disease,” Singh said.

The procedure for sending in samples is easy. Cut off one of the symptomatic fronds, take the leaflets off and put about one foot of the stem in a plastic bag and send it to your local LSU AgCenter county agent.

It normally takes from seven to 10 days to diagnose the disease, Singh said.

“If it is confirmed that a tree is infected, the only solution is to remove the tree from the soil and destroy it, preferably by burning,” Singh said.

Having these destroyed trees end up in mulch needs to be avoided because the spores are still viable and can infect susceptible palms it comes in contact with.

The economic impact of the disease could be substantial because the larger trees, which can live as long as 70 years and grow as tall as 60 feet, normally cost as much as $175 per foot.

Johnny Morgan

1/4/2011 1:10:57 AM
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