Surviving to Fight Another Day

Bill Lennon is working with researchers to learn more about survivor trees that are standing up to HLB.

Bill Lennon is a fifth-generation citrus grower who can recall the industry’s glory days when Central Florida had hundreds of thousands of citrus acres before the 1980s freezes pushed production southward in the state. But he’s remained dedicated to the area, managing his own groves and caretaking for others.

“I was born and raised in Orange County. My family’s citrus groves were located in east Orange County near the University of Central Florida area. I was raised in citrus, and that’s all I’ve ever done. And I committed to continuing growing citrus. At this point, I don’t care to write a resume,” he jokes.

After graduating from the University of Florida, Lennon went to work for ABC Fruit Company based in Orlando. He managed groves in Lake and Orange counties, all the way down to Fort Pierce.

“When the owner of ABC Fruit Company passed away, it worked out that I had the opportunity to buy the company out,” Lennon says. “So, since 2000, I’ve been operating the company as Lennon’s Grove Service.”

Between his own acreage and groves he manages for others, the company oversees about 900 acres in Central Florida.

WITNESSING HLB’S WRATH

Lennon characterizes his citrus career in two parts: half without HLB and the other half with the disease. “It has been about 17 years with it and the first 17 without,” he says. “That first 17 was a lot easier, and we’ve been looking for solutions ever since.”

HLB really started spreading through the area where Lennon’s groves are in the early 2010s. He said the last “good” crop was recorded in the 2012–13 season. That season, some groves yielded 600 to 700 boxes per acre. Since then, the crop has been in decline.

THE SURVIVORS

As HLB began to take its toll, Lennon started taking notice of some trees in one of his better-producing groves. The grove is in Lake County not far from Groveland. This season, it picked about 250 boxes per acre.

“This is one of my favorite blocks, so when I had an opportunity to buy into it, I jumped at the chance,” Lennon says. “This grove has been able to carry its weight relative to others, even during the HLB years. We are confident running a solid production program here because it’s better ground that seems to respond.”

Another thing he likes about the grove is that about 40 of the trees scattered throughout the rows have seemingly defied HLB over the years. They have declined, but not nearly at the rate of most other trees. These survivor trees easily can be picked out visually and they produce more fruit.

In 2016, word of these trees got to Gary England, who at the time was the citrus Extension agent in Central Florida. He went to see them and has been studying them ever since, although he was distracted from the project somewhat during an appointment to run the Hastings Agricultural Extension Center for two years prior to his retirement in 2020. But in retirement, he adopted the project to figure out what’s going on in these survivor trees. 

WHAT ARE THEY?

The grove was replanted around 1987 in the recovery from the 1985 freeze. It also was a period after a blight had gone through nurseries, requiring the destruction of stock. Trees were in short supply.

“During that timeframe, you kind of took what you could get from nurseries,” Lennon says. “So, there could be a hodgepodge of rootstocks and varieties out there. They are supposed to be Hamlin on Swingle.”

“The first tree we started following in 2016, there was no bench on it, so we were thinking it was definitely not Swingle,” England says. “As we were looking at some of these other trees, they were seedy, so that was ruling Hamlin out. But we also saw some trees that we believe are on Swingle, so it is still a mystery what they are. One theory we have is these trees were resets in that block soon after it was planted. At first, we thought the apparent HLB tolerance was a rootstock effect. After observations, we are not sure but can’t rule it out.”

In 2021, England recruited the help of Manjul Dutt, an assistant professor of horticultural sciences with the University of Florida Institute of Food and Agricultural Sciences, to learn more about the origins of these trees. The first step was to collect tree performance, yield and juice quality data from the trees. The yields have been impressive. This season, one of the better trees picked 10 boxes and 6 pounds solids.

“We plan to sequence the DNA from a subset of the consistently better-performing trees. This sequenced DNA will be aligned with DNA from several early-season sweet oranges residing in the Florida Department of Agriculture’s Division of Plant Industry’s (DPI) repository,” Dutt says. “This will shed some light on the origin of the cultivars as preliminary analysis seems to suggest that several scions may not be Hamlin.

“There is a combination of a yet unknown seedy early-season sweet orange and Hamlin in that block. Results of analysis of root tissue DNA in Dr. Fred Gmitter’s lab indicated that the rootstock of most of the survivor trees are true-to-type Swingle. However, some rootstocks are Swingle zygotic seedlings that originated either from self-pollination or cross-pollination of the seed source tree.”

DPI staff have collected budwood from four of the better-performing trees in the grove, and those have been entered into the agency’s parent tree program. A replicated field trial in several locations with some of the identified selections is planned to understand if the perceived tolerance to HLB can be consistently reproduced in other locations.

DPI’s cleanup process takes some time, but Lennon and England hope to get some of the “dirty” replications of the trees soon so they can plant a number in the grove on known rootstocks to see how they perform.

ULTIMATE GOAL

“We would love to take budwood from these 35- or 37-year-old-trees that seem to have HLB tolerance and put them on a commercial rootstock to see if that tolerance continues in the new trees,” England says.

Lennon credits both England and Dutt for taking an interest in these trees to learn more about why they have continued to produce, despite the presence of HLB. The initiative has been driven more by passion and curiosity than a budget funding the research. But hopefully, funds might come as more is learned.

“There was so much interest generated about the Donaldson tree in the past couple of years. I think more people might think there is something to these survivor trees,” says Lennon. “We talk a lot about bridging the gap between now and a solution to HLB. Maybe these trees can be part of that bridge.” 

Lennon believes the fight against HLB will be won. He and his wife Kim just purchased property in Putnam County to plant a new 20-acre grove.

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