Scientists, growers refine nutrient blends for HLB-infected trees

04/11/2013 03:10:00 PM
Renee Stern

While the citrus industry seeks better solutions to huanglongbing—also called citrus greening—growers can use nutritional programs to help keep greening-infected trees productive as long as possible.

Tearing out infected trees as soon as the disease is detected isn't always the most practical solution, says Fritz Roka, associate professor of agricultural economics at the University of Florida's Southwest Florida Research and Education Center in Immokalee.

"To make roguing work, you have to be very vigilant on scouting," he says. That means starting early and never letting up.

Replanting after tearing out infected trees leaves growers waiting two to three years for young trees to come into production, Roka says.

That was the calculation Maury Boyd, president of McKinnon Corp. in Oakland, made when he first realized his Orange Hammock grove was severely infected with greening.

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In 2006 the decline that he'd initially attributed to hurricane damage was diagnosed as HLB; 70 percent of the grove's young trees and 43 percent of his mature trees were infected.

"I was told then the trees would probably be gone in two to three years," Boyd says. "I didn't buy into the prediction of utter doom."

The tipping point had come and gone before he'd even been aware.

"We couldn't remove the infected trees," he says. "That would've been half the trees in our groves."

Nor would it be a solid long-term solution, with the rest of his trees probably infected but not showing symptoms. That, combined with infected groves on neighboring properties, meant any new trees he planted were certain to pick up the disease in a short time.

A ‘Mediterranean diet’ for trees

Growers in Western states, now on the alert after watching Florida deal with greening, may be able to avoid reaching that tipping point, Boyd says.

He focused on tree nutrition, supplementing a soil fertility program with foliar applications of what's come to be known as the Boyd cocktail full of minerals and other nutrients.

Controlling Asian citrus psyllid, which vectors the disease, also remains essential.

His trees now produce the same fruit yields as before infection, he says.

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Maury Boyd    
Florida  |  April, 15, 2013 at 05:15 AM

The article is well written. We apply the materials while the new emerging and expanding flush is developing, before maturity is reached and the cuticle forms. Of primary importance is for the materials to absorb into the new growth. Additionally, where we have poor soils, sandy and low CEC , we apply to the soil compost ( SWFla ) and recently have increased our soil application of calcium nitrate over that of ammonium nitrate. Regarding roots we find no P but have Fusarium ( secondary ?) found on blighted trees ( citrus blight a + 100 year old disease & cause is unknown ). This was confirmed for me when last year we reshapped our furrows ( recut every other middle, deeply, to increase water drainage ) and we found we had a heavy root system through out. Soil testing by all has been limited. Maury Boyd

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