A microscopic beetle is beginning to devastate native Southwest Florida trees, and the bug could eventually turn its sights on the avocado industry.
The redbay ambrosia beetle is not quite 2 millimeters in length, but the tiny insect can take down 40-foot bay trees in a matter of weeks.
The Asian beetle and laurel wilt disease were first documented in 2004 in Duval County in northeast Florida. Some experts think the beetle was brought to America on a shipment of tainted wood.
They basically drill holes into bay and avocado trees and feed on an invasive fungus, which, in turn, spreads a disease known as laurel wilt. Some chemicals can kill the bugs on farm fields, but there is no known large-scale method of removing the region’s latest crippling invasive.
Laurel wilt was found in Lee and Collier counties last year and is established in all but a handful of counties in the panhandle region.
“We’ve had a suspicion for about a year, that it was happening, they were dying, but apparently it can happen a lot sooner than that,” said Franklin Adams, a Golden Gate resident who has also seen the impacts of the disease in Big Cypress National Preserve. “They get into the white sap wood that’s under the bark. I haven’t seen one, but you see this sawdust and then you know they’re there. It disrupts the tree’s ability to function.”
Bay trees provide habitat for wildlife and produce a berry that’s eaten by a variety of birds and animals. Species found in Florida are similar to the bay leaf used to flavor soups and sauces.
The trees also have cultural and medicinal uses among indigenous cultures like the Seminole and Miccosukee.
The beetles spread at a rate of 20 to 30 miles a year, according to the University of Florida research, which also says the disease can be transmitted by hauling infected firewood into uninfected areas.
Stephen Brown, with the University of Florida’s Institute of Food and Agricultural Service in Lee County, said property owners who suspect they have laurel wilt should take samples of any potentially infected trees and have those inspected by a horticulturalist.
“With this type of situation you want real confirmation instead of guess work,” Brown explained.
The remains of a redbay tree are left behind from an exotic Ambrosia beetle. Laurel Wilt, a disease that infects red bay trees and avocado trees is killing trees in the Southeast including the Everglades and Southwest Florida. This tree is Golden Gate resident Franklin Adam's yard. (Photo: Andrew West/The News-Press)
Brown said visual indications of laurel wilt can includes dried up leaves, discoloration of internal wood and the presence of sawdust in the lower trunk.
“It looks kind of like sawdust or cigarette ashes, but that doesn’t last long,” Brown said.
University of Florida research shows that the beetles do more damage to larger avocado trees than smaller ones. Adams sees similar conditions on his land.
“We have a lot of little ones (bay trees),” Adams said. “The small ones, 4- or 5-feet tall, they seem just fine.”
Dead leaves and dark, vertical stripes under the bark layer are indications of infestation.
The condition is becoming more common in natural areas and preserves but is expected to impact the avocado industry because avocado trees are related to bay trees.
Female beetles are more common than males and can fly, which males cannot.
Chemical compounds like Danitol or Malathion can be used to kill airborne redwood ambrosia beetles, although the state recommends the chemicals not be used until laurel wilt is confirmed in particular farming operation.
Golden Gate resident, Franklin Adams checks one of his redbay trees that is dying from Laurel Wilt. The disease is caused by a fungus that is transmitted by the exotic redbay ambrosia beetle. It is killing redbay trees throughout the everglades and Florida.
Pruning trees can speed up infestation because the pathogen can be transmitted by hand saws, and because pruned areas of trees are more vulnerable to redbay ambrosia beetles.
Florida’s avocado crop is worth about $30 million a year and is the second largest in the nation.
The beetles haven’t crippled the avocado industry, but UF research suggest the bug may focus more on avocado trees after the bay trees have been decimated.
Avocado growers in this area say they haven’t seen evidence of the disease in their groves. Farmers like Gary Schneider, owner of Pine Island Tropicals on Pine Island, said he’s keeping his fingers crossed that the beetle stays off his land.
