Cobra, a black, 2-year-old female Belgian Malinois, leads the pack.
She is determined. Her ears stand on end as she focuses on her handler, Lourdes Edlin, who is holding a red ball. Cobra, who’s done this before, knows she’ll receive a reward — her favorite toy — if she sniffs out the small plastic bags of diseased wood hidden inside nearby trees.
The training isn’t for fun, but comes with loads of pressure — helping save Miami-Dade County’s avocado industry. Scientists and farmers believe dogs like Cobra can help slow down the crop’s decline. The avocado is the county’s leading crop, bringing in $54 million a year in revenue. But since 2012, more than 12,000 commercial trees have died from laurel wilt, a fungal disease spread by foreign, microscopic ambrosia beetles.
“Once infected, the tree, in hopes of saving itself, begins to wall itself off from the fungus and ends up actually killing itself,” said Charles LaPradd, the county’s agriculture manager. This is where the dogs come in — they sniff out the deadly fungus, letting scientists know which trees are sick.
12,000 Number of South Dade’s commercial avocado trees killed by laurel wilt since 2012
Cobra gets down to business. Her tail stops wagging; her eyes are fixated as she waits for her trainer’s signal.
“Search!” Edlin said in Dutch, a language commonly used to train dogs.
After about two minutes of roaming and sniffing, Cobra has a hit. She finds the sick tree and sits down abruptly to notify Edlin. She gets her prize.
“Good girl,” said John Mills, Cobra’s main handler and a South Dade farmer himself, as Cobra leaped on top of him, giving him a slobbery kiss.
Next up is her colleague, One Betta, who waits her turn in an air-conditioned van.
The tiny, brown, flying beetle — about one millimeter long — carries the fungus in its jaw. The fungus spreads to trees when the beetle digs through healthy tree trunks. It is fast moving. As the fungus spreads inside the wood, the tree turns dark brown and dies in about five weeks.
The fungus spreads to other trees because the roots of avocado trees connect underground over time. If one tree becomes infected, it can transmit the disease through the roots to the adjoining trees.
Laurel wilt first entered the U.S. from Asia in 2002, but it wasn’t until 2012 that it was found in South Florida commercial avocado groves.
Recommended protocol for a tree that appears infected by laurel wilt: Remove the tree by the root and burn it.
The insect does not like the avocado fruit itself, just the tree trunk. And although a tree may be infected, the fruit that was on that tree at the time is not.
Scientists at the University of Florida Tropical Research and Education Center, along with experts at the Miami-Dade County Extension, have developed a recommended protocol for anyone with a tree that appears infected: Remove the tree by the root and burn it.
But Mills wants that protocol to be a last resort.
Last year, he and his wife, DeEtta Mills — a DNA expert and Florida International University biological science professor — launched Innovative Detection Concepts, an FIU start-up company that uses dogs, drones and injections to slow down the crop loss as scientists continue to search for a cure.
The concept? Drones are used to monitor color changes that indicate stress in the trees’ canopy, then disease-sniffing dogs find trees that are affected even before they are symptomatic. That’s when a fungicide called Tilt is injected to help prevent infection.
We train the dogs on how to detect at the very earliest opportunity.
John Mills, Innovative Detection Concepts
“When we first heard about the laurel wilt spreading, I became concerned for our 180 acres of crop, that it may not be saved if we didn’t move quickly. That resulted in discussion of how we might use dogs for early detection,” John Mills said. “We train the dogs on how to detect at the very earliest opportunity and it’s now down to the day that the fungus arrives that we can find it.”
Humans have five million olfactory receptors. Depending on the breed, dogs can have as many as 300 million. Mills says the dogs have had more than 150 positive hits for laurel wilt.
Mills uses a combination of Tilt to kill the fungus and a natural fungus to kill the beetle.
Arthur Ballard, owner of the local Ballard Groves, had to remove about 80 infected trees. He partnered with Cobra and One Betta.
Surrounding the devastated area of dead avocado trees are healthy trees being injected with fungicide, something he says has helped him maintain healthy crops and slow down disease spread.
“It can be costly,” Ballard said, adding that he has spent more than $50,000 on removal and treatment.
Like many local farmers — some of whom cannot afford the treatment — Ballard isn’t replanting avocado trees.
“I’m replanting mamey instead,” he said.
Some larger farms are opting to replant avocado trees because the ambrosia beetles aren’t attracted to young trees, scientists say. Avocado trees don’t mature and bear fruit for at least five years. By then, they’re hoping for a cure.