This summer, there was great concern among commercial avocado growers in Redland (including Bee Heaven Farm) about the apparent discovery of the redbay ambrosia beetle, which rapidly kills avocado trees, and has been located in North and Central Florida. At least one tree in Redland was suspected of infestation and was burned. UF/IFAS held a workshop (which was blogged) giving information about the beetle and laurel wilt, the lethal fungal infection that it causes.
If you have avocado trees on your property in town, don’t think you’re immune. Learn what the signs are and watch your trees carefully. There’s good information at Save The Guac and the UF/IFAS sites.
Farmer Margie told me in summer that she will take a wait and see attitiude with her grove. Both she and Gabriele Marewski of Paradise Farms (who also raises avocados) are cautiously optimistic that a healthy, unstressed tree may not get infested and die. So far so good, fingers crossed.
Here’s a good follow-up article about the situation, published in the Miami Herald on Dec 26th.
This year’s avocado season is making farmers happy: The 920,000-bushel crop, grown mostly in southern Miami-Dade County, is fetching prices that are almost 50 percent better than a few years ago. But as the season comes to a close, those in the Florida avocado industry are casting a wary eye to Martin County, where the redbay ambrosia beetle continues its march southward.
Growers, scientists, and the local, state and federal governments are in a race against the beetle as it makes its way south to the $30 million avocado industry.
The beetle, believed to be a native of Asia, is described by scientists as smaller than Lincoln’s nose on the penny. But it carries a fungus that has proved lethal to many trees in the laurel family, including redbays and avocados, from the Carolinas through Georgia, and now Florida. There is no method to cure the disease.
After citrus, avocados are Florida’s largest tropical-fruit industry. This year’s crop was more than 50 million pounds, virtually all of that grown on 7,500 acres in Miami-Dade.
“The avocado industry is very concentrated in one area,” said Craig Wheeling, president of Brooks Tropical in Homestead, one of the largest growers, packers and shippers of Florida avocados. “It’s kind of an all-or-nothing fight down here.”
Wheeling said his best avocados were getting about $16 a bushel — 45 percent better than the $11-a-bushel prices three years ago. He attributed the higher prices to not just a smaller crop, but to growing demand for Florida avocados. And he said that’s what makes it even more crucial that scientists find a way to combat the beetle and the fungus-causing disease it carries.
Females carry the fungus spores in a special pouch within their mouths. When the insects bore into a healthy tree to check if it would be suitable for nesting, the tree is inoculated with fungi that cause a disease called laurel wilt. As it spreads, the tree’s water system is disrupted, causing the leaves to wilt so quickly they don’t even fall off.
The larvae and adult females feed off the fungus — essentially, the beetle carries its farming system with it, said Jonathan Crane, a tropical-fruit plant specialist with the University of Florida’s Institute of Food and Agriculture Sciences in Homestead.
There are dozens of varieties of beetles that have a symbiotic relationship with a fungus it carries. The one beetle/fungus combination that has proved deadly to the redbay and Florida avocado tree is a specific variety with the scientific name raffaelea lauricola. It was first detected in Georgia in 2002.
It took a few years to spread through Georgia and was first found in Florida’s northern counties in 2005. On its own, the beetle can fly about 20 miles.
It has spread exponentially quicker the past two years to Central Florida, experts believe, because diseased trees have been cut down for firewood and brought south.
In late July, the local industry panicked after the state issued a press release saying a confirmed case of the beetle had been found in a Homestead grove.
Growers, including Brooks, spent hundreds of thousands of dollars to cut down and burn trees that looked weak or infected, and to spray groves with extra pesticides.
That initial test proved to be a false positive because the science behind tracking and typing the fungus is just developing, said University of Florida forest pathologist Jason Smith. The beetle and fungus have never been studied in Asia, where it is believed to come from, because trees there haven’t died.
“Nobody had ever looked at this,” Smith said.
It took weeks to confirm that the disease hadn’t reached Miami-Dade. Even so, the industry remains on guard.
“It’s still a threat,” said Miami-Dade County’s agricultural manager Charles LaPradd. “What I would love to say is that it will never get down here, but that’s fantasyland.”
Local growers say what happened this summer was a test.
The summer scare caused growers to start regular meetings with local, state and federal agriculture officials and scientists, who said they are close to a method that would confirm the disease in a day or so.
Most of the research is being spearheaded by the University of Florida, which received a $1.2 million USDA grant to find a way to beat the beetle.
One possible method might involve sterilizing the large equipment that is used within groves to prune trees, Smith said. Others are looking at the natural resistance that has been found in Asia and among some local varieties of trees. Additional research is going into fungicides that need to receive federal approval before being used.
In the meantime, the state agriculture department has also started a marketing campaign based on one of the fruit’s most popular uses, guacamole, at www.savetheguac.com. It’s designed to help educate the public about moving firewood and how to spot diseased trees.
“There are tens of thousands of backyard avocado trees in South Florida,” said state agriculture spokesman Mark Fagan.
“We can’t go into every backyard and inspect every avocado tree — we need the public’s help.”