As Boyd has, Rouse applied macronutrients by ground and made foliar applications of micronutrients and systemic acquired resistance-inducing materials during each tree flush.
“My feeling was we might be able to save those two commercial groves that had up to 50 percent infection, but the one here I didn’t expect to pull out of it. But citrus trees have great recuperative power.
“My whole deal was if this comes back, it will be a miracle. The other two I really had hopes for.”
As an offshoot of the study, Rouse says in 2009 he began an extensive study of the roots of the trees treated with the Maury Boyd cocktail compared with the untreated trees.
“We found that we were not losing root density or root mass,” he says. “We didn’t have sloughing or declining roots.”
The study involved collection of 1,000 samples from among nine different treatments and five reps.
Rouse repeated the sampling in 2010 and found trees that received the Maury Boyd cocktail actually had increased root density compared with 2009 results.
A balancing act
The initial trial results prompted Rouse to consider whether buckhorning a tree to bring the canopy more in balance with a smaller root system, then feeding it with the micronutrient mix, would be a viable alternative to tree removal.
In 2010, he established a trial at the SWFREC that compared various nutritional regimes applied to both unpruned and buckhorned trees. The buckhorned trees were mechanically hedged and topped to 4 by 4 feet.
“If it works, then a grower could set up a strategy to rehabilitate through pruning some percentage of his grove every year until it was back into production and it wouldn’t totally eliminate his cash flow,” Rouse says.
A buckhorned tree should regrow and be back in production within about two years, he says. But a replant typically takes four years to come into production and another three years to where production will repay the investment.
Even though the buckhorning removed most of the 2010 crop, Rouse says they still harvested 1/3 box from each tree that received the severe pruning and the nutritional sprays the first year.
That compares to 1/4 box per tree average before buckhorning.
Trees that were left unpruned but received the nutritional sprays yielded 1/2 to 2/3 box each.
Boyd and grove manager Tim Willis, who are closely following Rouse’s trials, buckhorned trees in January in part of a grove with the poorest soil near Felda.