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(For the week of July 26, 2010)
Ambrosia Beetle
by James L. Cummins

A tree-killing Asian beetle smaller than a grain of rice has begun eating its way through Mississippi’s coastal forests and is likely headed for Alabama.

The ambrosia beetle targets the ubiquitous red bay and close relatives in the laurel family, such as sassafras. Scientists say it has the potential to completely wipe out some of the most common trees in the swamps and wetlands along the Gulf coast. By some estimates, hundreds of trees have already died along the Pascagoula River.

The beetles bore pinhead-sized holes into the trees, and then munch on the soft wood just under the bark. But that is not what kills the trees. The beetles carry a fungus that infects the trees and prevents water movement from the roots into the crown, according to scientists. Starved of water, the trees die, their leaves wilting and turning brown, giving the disease its common name – laurel wilt.

“Red bay is a major component of the forest understory in the bay swamp habitat,” said Will Underwood, a wildlife biologist with the Grand Bay National Estuarine Research Reserve. “They produce a fairly large berry that is used by birds, squirrels, bears, all kinds of wildlife. Their absence will be a big deal in the forests around here.”

Underwood said he has seen a few trees around Grand Bay that appear to show early signs of infestation, which would mark the first appearance of the disease in Alabama.

Similar fungal diseases carried by other kinds of beetles were responsible for virtually wiping out chestnut trees and the American elm. Decades later, efforts are under way to restore both species, and scientists said it might be possible for the red bay to rebound at some point in the distant future.

There is no known cure or antidote for the fungus, which is native to Japan, India and Taiwan.

Scientists believe the beetles arrived in the U.S. via shipping pallets or containers arriving at coastal ports. First discovered in 2003 in South Carolina, laurel wilt had spread to Georgia and Florida by 2005. A paper produced by Florida scientists at the time says that all red bays above 6 inches in diameter died in the affected areas. The paper’s subtitle is “Extinction of Red Bay Trees in the Southeast.”

It is possible the Mississippi infestation began with an infected shipment arriving at the port of Pascagoula. Scientists were surprised when the disease was discovered at several locations in Jackson County, as there hadn’t been any sign of it along Florida’s Panhandle or in Alabama.

James L. Cummins is executive director of Wildlife Mississippi, a non-profit, conservation organization founded to conserve, restore and enhance fish, wildlife and plant resources throughout Mississippi.