Wednesday, November 14, 2018
News Roundup

Drones and dogs save suicidal avocados from the dreaded redbay ambrosia beetle

REDLAND

Foreign invaders are decimating Florida avocados.

Standing between the avocados and their attackers is an innovative detection program at Florida International University. Scientists fly camera-laden drones over avocado groves in order to direct disease-sniffing dogs to infected trees.

Florida's avocado industry is small, 7,400 acres in production, with a value of about $13 million annually, although its economic impact hovers around $54 million if you include farm and farm-related jobs like packinghouses. Chump change. Consumers and Florida officials may be unflustered about the avos' plight in light of our other agricultural battles: Citrus greening! The invasion of giant African land snails!

But pull back, and you'll see California's avocado industry is 10 times larger than Florida's. Mexico's is 100 times larger. Farmers in both places are terrified of what destruction the redbay ambrosia beetle might wreak. They have reason to worry — the beetles are on the move, having been found as far north as North Carolina and as far west as Texas.

If we do nothing, kiss our guacamole goodbye.

More than 90 percent of untreated trees die within six weeks of infection. DNA expert and FIU biological science professor DeEtta Mills says an estimated 500 million trees in the laurel family, avocados its main commercial species, already have died.

There's a front line in this battle and it's 20 acres in Redland, an unincorporated community in Miami-Dade County. This may sound like the plot of a dystopian movie, but stand in the grove, and you'll see the action is real.

 

Sci-fi/horror

The beetle hunkers down, a stowaway from Myanmar or maybe Indonesia. Riding in on untreated wood, perhaps a crate or a pallet, it bides its time, with a ticking time bomb stored in a pouch on the top of its head.

The year is 2002, or is it 2003? Either way, it moves methodically.

Zoom in. The size of a grain of rice, the shiny brown segmented creature bores a matchstick-sized hole in the trunk of a tree in the laurel family. It reaches into its pouch and pulls out the spores of a fungus called Raffaelea lauricola, inserting the spores into the empty space. The beetle's aim is to incubate the spores, farming the fungus as food for itself and its offspring.

As in Alien, this invader isn't overly concerned about the well-being of its host. The tree senses the intruder pathogen and begins to shut down its own vascular system, trying futilely to wall off the spreading spores. Like a cancer, spores proliferate just as the host tree starves itself of water and nutrients.

In the woods of Georgia or South Carolina it's a quiet death, withsassafras and pondberry trees going brown, largely unnoticed. The beetle doesn't mind; there always are more trees.

By 2007 the fungus was here in Florida, entering Duval County, then Indian River, Brevard, Okeechobee, Osceola and finally creeping into Miami-Dade, the center of Florida's commercial avocado production. And the avocados started dying.

 

Boy and his dog

The drone weaves nimbly and sounds like an angry dragonfly. It's an $800 white DJI Phantom, an early model, two of its four copter propellers painted orange so the high school students know which end is the front end.

Zachary Fitzgerald, a senior, operates the controls while sophomore James Bateman functions as a spotter in the long rows of trees. The FAA requires that they maintain visual contact with the craft.

The boys showboat a little, the craft swooping and diving, until their teacher Gustavo Junco, who teaches agriculture and drones in the environmental science magnet program at South Plantation High School, chides them mildly. Not too high.

The program's regular drone operator has been called away on other work. In his place a team from the school has been tapped to run the day's drone exercises on Art Ballard's 20 acres in Redland with two camera-mounted copter-style drones.

As drone pilots, teenage boys are hard to beat: In a recent competition video gamers trounced trained military pilots in maneuvers. They are joystick superstars. These boys in particular have herded goats using drones and took first place in the obstacle course at a recent drone competition.

"I like flying for recreation," Fitzgerald says as he practices doing a wide figure-eight 100 feet overhead. "But if I can help out with agriculture, why not?"

The students' drones monitor color changes that indicate stress in the trees' canopy, then disease-sniffing dogs race in to assess which trees are affected even before they are symptomatic.

Nearby, four trees into a row of avocados, Cobra squats. Is it a positive identification? No, pee break. So it goes when your investigator is a 2-year-old female Belgian Malinois.

Dog handler Lourdes Edlin gets Cobra back on track, and 10 trees deeper into the row, there's a hit.

This was supposed to be a training exercise. Edlin had planted some bags of diseased wood in tree knots to hone Cobra's skills and those of her colleague, One Betta, who waits her turn in the air-conditioned van.

But Cobra is adamant. This tree smells sick.

Dogs have 300 million olfactory receptors; humans have 5 million. Col. John Mills, who owns Innovative Detection Concepts and is married to Dr. Mills, provides the dogs to the program. He says these dogs have had 103 positive hits for laurel wilt.

Because an avocado tree can suffer from myriad other problems — drought, lightning strike, root rot, fruit load, etc. — Dr. Mills says dogs' sniffers provide the "ground truth" of data that drones have collected from above.

If she's right, Cobra makes it 104 positive hits.

 

Historical drama

On Super Bowl Sunday this year Americans ate 80 million pounds of guacamole. Avocado is now near the top of the heap of fruits eaten in the United States.

These are mostly not Florida avocados. Why not? According to Jonathan Crane, a tropical fruit crop specialist at University of Florida IFAS, it's about marketing.

The black-skinned Hass avocado, grown in California, Chile, Peru and Mexico, has a consortium that does their marketing. You don't see TV ads for the green-skinned Guatemalan-West Indian hybrids Florida grows, 98 percent in Miami-Dade.

Still, Florida avocados started early, at the end of the 1800s.

Pioneers planted seedling trees, but as the popularity and demand for the fruit increased, the Florida industry pioneered grafting propagation of avocado trees, Crane says.

In the 1930s and '40s, the USDA in Miami introduced seedling avocados from Mexico and the Pacific Coast of Central America. They brought back seed from different varieties of avocado, planted the seed out at the USDA station, and they crossed naturally. The USDA then gave seedlings to local growers.

The market for them is specific: Latin Americans, Caribbean islanders and longtime Floridians. The state doesn't export them to other countries, but they find their way across the country, even to California.

Green- and black-skinned avocados, says Crane, have two different audiences. Fans of the green-skinned like the flavor and size.

The irony: Before the emergence of laurel wilt, the USDA in Miami and in Fort Pierce implemented a program to develop varieties similar to the Hass, those adapted to growing conditions in South or Central Florida, with the aim of helping the state's farmers beset by citrus greening.

Crane, for one, is not giving up on Florida avocados. The University of Florida just received a $3.4 million grant to investigate a number of aspects of laurel wilt.

"If you can intervene more quickly, you can be more effective."

And as far as Dr. Mills and environmentalists are concerned, laurel wilt has ramifications far beyond the financial imperatives of the avocado industry. Songbirds, turkeys, quail, deer and the palamedes swallowtail butterfly depend on laurel family trees for food and shelter.

"We're going to lose a lot of habitat. This ecological disaster is bigger than the economic one."

 

The romance

Ballard started noticing laurel wilt on his farm a year and a half ago. To date he has lost 30 trees in a grove that has been in his family since the early 1900s. That makes it one of the oldest groves in the county. It's not many trees, but a mile away at the corner of 147th Avenue and Eureka, an 80-acre plot has been decimated, the absentee owners giving up the grove as lost. One strong wind … and ambrosia beetles have the means to hop.

Ballard puts things in perspective: Once a farmer has been alerted to ambrosia beetles and their fungus, it costs $1,200 per acre to treat with fungicide. Florida avocados are what some experts call a "low margin" crop. To not treat may make economic sense, but as with non-vaccinating parents, that may put neighbors at risk.

He is considering tearing it all up and replanting in limes or papayas. In a battle between his heart and his wallet, Ballard is at a crossroads.

So, too, is FIU's disease dogs and drones program.

Funded with a grant from the Florida Department of Agriculture, the idea for the program came out of a conversation last year between Dr. Mills and FIU provost and forensic chemist Kenneth Furton, who is a canine scent detection expert.

The collaboration is between dogs and drones, but also between academics: In the lab, Mills and her students do the DNA work, looking at the biology of the fungus and the response of the trees. Furton and forensic chemistry graduate student Allison Simon are working on creating mimics of the dominant odors so that they can safely and more effectively train the dogs.

It took nine months to train Cobra and the two Dutch shepherds currently certified in the program; three other dogs are in serious training and two more rescues have been identified as promising. According to Simon, it's more complex to train a dog to do this kind of detection than drug or explosive sniffing. (Plus, you have to teach dogs not to eat the avocados.)

Other applications for the drones-and-dogs duo are also at stake. Simon says training dogs to a new scent is analogous to introducing new vocabulary. The park service is exploring the idea of training dogs to sniff out invasive plant species, and other scientists are considering this approach for detecting an invasive flatworm that is killing Florida's snails.

In March, the grant's funding runs out. Unless money is found to continue the avocado program or to retrain the dogs, Cobra and friends will be unemployed. Col. Mills is worried.

"You can't just put these dogs back on the shelf."

Farmers can't treat a problem they can't see.

And beyond Miami-Dade's groves, the beetles march on.

Contact Laura Reiley at [email protected] or (727) 892-2293. Follow @lreiley.

     
         
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