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
March 21, 2017
Industry Groups, Ag Leaders React to Proposed USDA, EPA Budget Cuts
New plan would slash USDA spending by 21%. Read More
fork digging into a plate full of salad
Citrus
March 21, 2017
Since When Did Eating Get So Complicated? [Opinion]
The bottom line to all this is the way we eat is undergoing massive disruption. Read More
Swadesh Santra of UCF
Citrus
March 16, 2017
UCF Stepping up to Be Farming’s Knight in Shining Armor
Hopes are high that the school's new agriculture research center will help growers solve production issues and feed the globe. Read More
A.H. Whitmore Farm in Leesburg, FL, as seen from Google Earth
Varieties & Rootstocks
March 16, 2017
Experimental Citrus Groves Disappearing in Florida
Challenges to growth expand as vital research is in dire need of a home. Read More
Frozen blueberries
Berries
March 15, 2017
Arctic Blast Gives Southern Fruit Growers the Chills
Peaches and berries in bloom most at risk from freezing temperatures. Read More
Citrus
March 15, 2017
Group Wants To Streamline Food Safety Regulations
There are 15 federal agencies implement more than 30 different food safety statutes. A team of experts believe they have a solution. Read More
Cutting the power cord
Citrus
March 14, 2017
Can Your Farm Survive If the Grid Goes Down? Can You?
Even in a plugged-in world, the basics are needed now more than ever. Read More
Stormy skies over Florida
Citrus
March 14, 2017
Concerns Mount in the Sunshine State Over Growing Rainfall Deficits
Water conservation efforts called for as the dry season rolls on. Read More
Citrus
March 10, 2017
Jim Gorden Named California Citrus Research Board Chairman
Gorden, who previously served as chief of the California organization, was a partner in the first independent citrus pest management consulting company in the San Joaquin Valley. Read More
Florida citrus grove
Citrus
March 9, 2017
Florida Citrus Crop Besieged By Sinking Feeling
Latest USDA estimate yanks healthy chunk out of projected yield for oranges. Read More
Banding dry fertilizer on a potato field
Citrus
March 7, 2017
The Andersons Divests Florida Farm Center Locations
Local, family owned custom blend fertilizer company taking over assets and product distribution responsibilities. Read More
Suzanne Wainwright-Evans speaks to crowd at Biocontrols USA West 2017
Citrus
March 6, 2017
More Growers Willing to Bet on Biocontrols
Industry event highlighting alternative pest management methods draws interested crowd to Reno. Read More
Florida red grapefruit samples
Grapefruit & Specialty
March 1, 2017
Is South Korea a Grapefruit Market Goldmine?
Researchers are finding high demand for the tart citrus, opening the door for opportunistic Florida growers to fill the need. Read More
Citrus
February 28, 2017
Trump Set to Ditch Controversial Water Rule
WOTUS could be on the way out after an executive order calls for a top-to-bottom review. Read More
Florida citrus grove
Citrus
February 25, 2017
Citrus Research Investments Yielding Positive Results
Despite still having mounds of wood to chop, grower, federal, and state programs collectively are making a dent. Read More