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Beetle destroying redbay trees

Citrus County Chronicle

Published:   |   Updated: September 4, 2013 at 10:59 AM

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It's a speck of a beetle, barely as big as Abraham Lincoln's nose on the penny, but the damage it is causing has reached epidemic proportions.

It bores its way into the innards of a redbay tree through a pinhole-sized opening and goes on to introduce a fungus that moves to promptly kill the tree.

The deadly fungus is called laurel wilt because redbays belong in the laurel family of trees.

When the bark is peeled off an infected tree it reveals a dark brown wood rather than a lighter shade. The leaves will also wilt brown.

Redbays in the Southeastern U.S. are under assault from the ambrosia beetle, said to originate from Asia.

The fungus can kill nearly all mature redbay trees in a stand within three to five years, according to the Florida Forest Service.

The service said at one site in Florida, mortality of monitored redbay trees greater than 1 inch in diameter increased from 10 percent to 92 percent in just 15 months.

According to Kimberly Burch, the senior forester in Citrus County, entomologists began seeing dying redbays in southern South Carolina a decade ago and slowly the stand of wilted redbays began showing up southward into Florida.

"We first saw it in Citrus County on Gospel Island Road in 2009," Burch said.

"The fungus will attack what I will call the plumbing system of the tree and restrict the movement of water and food," Burch added.

She said by disrupting the flow of the flow of nutrients in the stem of the tree, the fungus quickly kills it. A tree can die in a matter of weeks, Burch said.

And, according to Burch, scientists are scrambling with pilot projects in hopes of coming up with a counter to arrest its spread.

Researchers are currently using a fungicide, which is injected in the root system of the redbays to help prevent the fungus from getting a hold.

Burch said that work has shown some promise, but so far nothing seems to be slowing the spread of the fungus.

Eric Hoyer, an arborist and consultant with Natural Resource Planning Services Inc., said he and his wife first noticed the infestation in the county about two years ago.

"It is pretty bad in Fort Cooper State Park," Hoyer said.

"It kind of stands out when you see a lot of wilted brown leaves in a sea of green," he added.

The rest of the state is not faring any better. Most of the state's counties are showing signs of the fungus.

"I found out that Hernando County has also been affected. I think we are yet to get any confirmation of cases in Pasco County, which would make them the only county in this area that has not been affected," Burch said.

She said a few counties in the southeast corner of the state have been spared - so far.

Laurel wilt is also known to attack avocado, sassafras and pondspice.

The following strategies may help reduce the spread and impact of laurel wilt:

Avoid the movement of firewood, tree trimmings or mulch from redbays and other laurel family hosts out of counties in which laurel wilt is known to occur.

Avoid long-distance transport of firewood in general.

Whenever possible, leave wood from dead and dying redbays and other laurel family hosts on site instead of transporting it. If the wood is to be transported, dispose of it as locally as possible.

Burying, covering, burning or chipping host tree material at its original site or a disposal site is preferable to leaving it intact in the open environment.

Chipping wood from an infested tree might not destroy all of the ambrosia beetles due to their extremely small size, but should reduce the suitability of the wood as breeding material.

Although the pathogen has not yet been documented to spread by this means, consider cleaning/sterilizing saws and pruning blades after cutting an infected tree and before using them on uninfected host tree species.

Nursery stock in the laurel family showing signs of wilt, sapwood discoloration or ambrosia beetle attack should not be sold or transported, and should be reported to the division of plant industry.

Preliminary research suggests that root-flare injections with the systemic fungicide propiconazole may help prevent development of laurel wilt in redbay trees.

Source: Florida Forest Service

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