Florida Citrus Grower Keeps His Cool In The Heat Of HLB

About 15 years ago, Rex Clonts got out of the vegetable growing business after many years to “retire to the easy life” of a citrus grower. But, the onslaught of HLB has turned the easy life on its ear and requires management more akin to row crops these days.

Years as a vegetable grower taught Clonts mechanical skills, which he hopes will serve him well trying to grow citrus in the presence of HLB. He is putting those skills to work to create a viable and systematic approach to utilize thermotherapy for treating HLB-infected trees in his grove — literally heating HLB-infected trees up to 130°F.

Dr. Yongping Duan, a researcher at Ft. Pierce’s USDA Horticultural Lab, is among those studying thermotherapy as a means of killing the HLB bacteria in citrus trees.
“I went down to visit Dr. Duan to learn about his research and then went back to my experience in making machinery that we used to grow and harvest vegetables,” says Clonts. “There are growers out there trying heat therapy, but nobody is trying to design a system that can be used industry wide on all-sized trees.”

Rex Clonts Photo by Frank Giles
Rex Clonts Photo by Frank Giles

Clonts says his goal is to build a system capable of treating 100 of his acres per summer with a crew of no more than four people. The setup would include a string of tent structures capable of treating an eighth of a mile (600 to 650 feet depending on grove layout). In Clonts’ grove, that would take 26 modules covering 52 trees.

“If this is ever going to be adopted by the industry, it must be simple and systematic,” says Clonts. “It needs to be predictable enough that when the four-man crew shows up in the morning, they know exactly what their duties are for the day and can go perform them efficiently. And, everything I am using to build these tents is commercially available materials sold for greenhouse production.

“Using this very systematic approach, you would operate enough of these units to treat a third of your acres per year. The theory is the heat treatments provide positive benefits to the tree for two to three years. If you are treating a third of your acres per year, by the fourth year, you would be starting back over as the benefits begin to wear off.”

Another key to the system is the ability to treat large trees, which require much larger tents than what many growers have seen in action to date with smaller trees. Clonts has built two prototypes and a third is planned, which will be slightly smaller and easier to manage. Clonts gable-cut tops his trees at 12 to 14 feet, so the tents must be sized large enough to accommodate the height.

Time And Temperature

Clonts began actively treating his grove in June. The goal is to capture solar energy in the tents and maintain temperatures at 105°F to 130°F, which research shows will kill the HLB bacteria.
“Right now our rule of thumb is we keep the structure over the trees for three days, seeking 10 hours per day of temperatures more than 105°F,” says Clonts. “One of the big things we’ve learned is the heating is very different over these mature trees than if you just put the tent out over a grass field.”

The canopy and moist soil surface have a moderating effect on the temperatures inside the tent, making air circulation critical to the process. Clonts fixed this challenge by installing circulating fans in the tops of the tents to move air.

“In these big structures, if you don’t move the air with the fans, you are going to only heat the top of the tree and possibly damage it, and the bottom canopy is never going to get heated,” he says. “We are finding that one fan per tree in the structure takes care of this problem.”

To ensure temperatures are monitored correctly, three standard digital thermometers are placed inside the tent at two feet, six feet, and 12 feet in the canopy. When temperatures get too hot, a thermostat in the structure engages an automatic venting system.

“The automatic venting system is counter-intuitive because we have a motor that keeps the vents sealed until we hit the critical temperature of 130°F,” Clonts says. “When it hits the temperature, the motor shuts off and the vents open. We do this because we want the tents to self-vent if we lose power. When the temperature drops back to 125°F, the motor starts back up and closes the vent.”

Topics: , , , ,

Leave a Reply

One comment on “Florida Citrus Grower Keeps His Cool In The Heat Of HLB

  1. Three years of positive results ( doubling the yields & increasing the solids count ) has proven that treating severely infected trees with all natural, non-toxic Quantum Growth would be a lot cheaper method using the thermotherapy approach.

Citrus Stories
Citrus greening and psyllids
Insect & Disease Update
June 21, 2017
First Case of Deadly Citrus Disease Confirmed in Alabama
State agriculture officials taking action to assess and stop the spread of HLB.  Read More
Florida orange juice label close-up
Citrus
June 21, 2017
Help Consumers Read past Negative Headlines About Orange Juice
When it comes to this liquid sunshine, there are plenty of positives to point out. Read More
Citrus
June 19, 2017
$9M in Grants Allocated to Address Ag Water Resources Issues
Projects that focus on drought stress, flooding, water quality, and postharvest use are among awardees. Read More
Citrus under protective screen
Citrus
June 19, 2017
How to Get the Most out of Growing Citrus Under Protective Screen
2017 Citrus Achievement Award winner Ed Pines provides insider information on unique production method. Read More
'Gold nugget' seedless tangerine
Varieties & Rootstocks
June 19, 2017
Florida Growers Seeking to Strike Citrus Gold
Varieties showing HLB tolerance giving growers hope, sparking more questions. Read More
Illustration of CRISPR-Cas9
Citrus
June 15, 2017
Make Way for Life-Saving Science on Your Farm [opinion]
While nature always finds a way to adapt, science continues to find other ways to cope. Read More
Jellyfish genes causing citrus phloem to glow
school lunch tray full of Florida-grown blueberries and watermelon
Citrus
June 15, 2017
Florida Farm to School Initiative Makes New Strides
Connecting with local growers, communication, and flexibility are keys to a successful nutrition program. Read More
Business Planning
June 14, 2017
How Ready Pac Went from Near Bankruptcy to Innovation in 3 Years
The company's new CEO, Tony Sarsam, spoke at United Fresh's MKT Expo about how investing in staff, increasing communication, and reaching for the same goal can transform a business. Read More
FL Gov. Rick Scott signs a bill
Citrus
June 9, 2017
State Budget Cuts Threaten to Take Big Bite from UF/IFAS Programs
Gov. Rick Scott’s proposed plan includes trimming more than $6 million from research and education-based initiatives. Read More
Citrus
June 9, 2017
Agriculture Water Standards Compliance Dates Extended
FDA says the agency will extend the compliance dates after feedback from stakeholders. Read More
Flooded vegetable field in South Florida
Citrus
June 7, 2017
Super Soaker Deleting Drought Status in the Sunshine State
From famine to feast, Florida’s record-setting dry spell has given way to a wide-open wet season. Read More
Center pivot irrigation system at Florida research farm
Citrus
June 1, 2017
Big Bucks up for Grabs to Water-Wise Florida Farmers
St. Johns River Water Management District cost-share funding would support implementation of conservation-minded practices and technologies. Read More
Citrus
May 30, 2017
Devastating Citrus Disease Found in Orange County, California
HLB detected in plant material from residential neighborhood. Quarantine expanded. Read More
Hurricane season photo collage
Citrus
May 29, 2017
NOAA Betting on Another Busy Atlantic Hurricane Season
Forecasters predict above-normal storm activity, depending on El Niño's naughtiness. Read More