Pumping Up Trees in the Face of Disease

Foliar nutrition takes on enhanced role in the battle against HLB

Since HLB (Huanglongbing) was first identified in Florida in 2005, its spread has been rapid across all citrus-producing counties in the state. Today, the disease is entrenched with ever-increasing rates of infection as scientists seek solutions for one of the citrus industry’s biggest threats.

“The infection rates are high,” says Ryan Atwood,  a former product representative for Winter-Park, FL-based KeyPlex. “We are getting pretty close to 100% infection rates in some of the worst-hit areas. It varies and is not as bad in the northern producing areas, but it is a quick-moving disease.”

Atwood has worked trials at the Mid-Florida Citrus Foundation at the Water Conserv II in Winter Garden, where HLB inspections basically show the disease tends to double in year. Within a three-year period, infection rates shot up to 60% in the grove located there.

“With the rapid spread of HLB, growers realize they had to come up with a better alternative than strictly tree removal to help rid groves of inoculum,” says Atwood. “For some big growers with big groves, they have had success with tree removal. However, if you look at the Florida industry, it is made up mostly of a lot of smaller growers with lots of neighbors, plus we didn’t get an early start in addressing the disease here. That just made the tree removal only approach not practical for many growers here.”

Growers React

Having worked as a researcher with the University of Florida, Atwood says he’s seen firsthand how growers are innovators in coming up with ideas to address problems in their groves. The onset of HLB illustrated the ingenuity as growers began to test enhanced nutrition programs in groves to help slow the rate of decline of trees infected with HLB.

“What happens a lot of times is growers are out in their groves trying new things and they bring it to one of the researchers at the university to run trials on the idea,” he says. “With the data from trials, it gives other growers more confidence to try something new.

“You look at what Maury Boyd did with enhanced foliar nutrition in his groves, which is credited by many as really focusing attention on this approach. Dr. Bob Rouse at the Research and Education Center in Immokalee took Boyd’s program, ran trials on it, and showed that other growers can replicate his approach. And, it has proven to work in helping to maintain the productive life of groves highly infected with HLB.”

Today, growers have created many different foliar nutrition programs to help stave off the effects of HLB. Atwood estimates as high as 90% of acres are on some kind of foliar nutrition program. “I would say these different foliar nutrition approaches have been mostly successful,” he says. “With HLB, if a tree faces any kind of stress like drought or a freeze, it will fall off quickly. The enhanced nutrition helps those trees stand up better to stress.

“But, it is more than just foliar nutrition. These growers have to be great managers running a good production program, whether it is irrigation or how they are dealing with other diseases and issues. In addition, psyllid control is an absolute must in any of these programs.

According to the state of decline, it takes some time to begin to see the benefits of enhanced nutrition, but initial signs begin to appear after the first year. “Most growers will tell you need anywhere from two to three years to get a tree back from going into decline,” says Atwood. “Again, this is without major stresses like a freeze or other disease problems and taking into account the grower is employing an overall good management program.”

As for KeyPlex, Atwood says they have a standard recommendation of five applications per year with its product, which includes a pre-bloom, post-bloom, early summer, mid-summer, and a fall application, along with partner products.

“Most enhanced nutrition programs include a strong micronutrient package like KeyPlex, and that includes a quality phosphite and a good NPK package. We often recommend Nutri-Phite (Biagro Western, Visalia, CA) because we consider it a quality phosphite and the NPK varies depending on the time of year.”

While many citrus fertilizers are available, studies show that KeyPlex micronutrient products are effective in reducing the effects of HLB by supplying key micronutrients. For more about KeyPlex citrus solutions, visit http://www.keyplex.com/crop-keycards/citrusoranges.html.