Although a field trial indicates that microbial soil amendments didn’t seem to help trees with HLB, the trial project manager sees a take-home message for growers. That message is that “well-managed trees can continue getting along OK,” says Jim Syvertsen, a scientist with the Citrus Research and Development Foundation. Syvertsen summarizes results he presented at a recent field day in a Premier Citrus Management grove near Fort Pierce.
“We’re at the third year of the study; it’ll be winding down at the end of harvest this year,” Syvertsen says. “These are all Valencias on Swingle. They’re almost 6 years old. The trees look amazingly good for having HLB. The trees are very well cared for” and have received good nutrition and good psyllid management.
“What we did starting in 2014 was to begin the soil microbial amendment trial with five different soil amendments superimposed on the background of good tree management,” Syvertsen says. “After 2.5 years, none of the microbials really stands out as different from the others and (there are) very little differences from the untreated controls. Those untreated controls are maintaining yields and canopy growth along with the other treatments.”
“One of the only differences is that the microbial-amended trees look a little bit better than the untreated controls,” Syvertsen says. “They have fewer visible disease symptoms even though all of the trees have HLB … But, again, no significant difference in the growth or yield.”
Syvertsen tells why he expected more benefit from the amendments. “Lots of growers have observed positive effects of soil amendment microbial products,” he says. “Researchers have shown that when a tree becomes infected with HLB and the roots begin to decline, there can be a change in the soil microbial constituents … and the microbial amendments are intended to restore the balance of microbes in the soil. But, again, here they had very little effect.”
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