HLB and Citrus Nutrition

Tripti Vashisth shared results of research into nutrition needs of citrus trees with HLB during a recent virtual educational program sponsored by the Citrus Research and Development Foundation and Florida Citrus Mutual. Vashisth is a University of Florida Institute of Food and Agricultural Sciences horticulturist at the Citrus Research and Education Center in Lake Alfred.

Here are a few key take-home messages Vashisth offered:

• HLB-affected trees benefit from micronutrients at a higher-than-recommended rate.
• A 20% higher-than-recommended rate of micronutrients can improve productivity of HLB-affected trees.
• Iron and zinc treatments are performing better in an Arcadia, Florida, research location.
• Manganese treatments are performing better in a Ft. Meade, Florida, research site.
• Soil-applied nutrients are better than foliar micronutrients.
• Magnesium, sulfur, boron, manganese and nitrogen improve fruit quality.

Vashisth said a constant supply of nutrients is beneficial to HLB-affected trees because those trees are significantly low in root and shoot biomass.

THE PROPER SOIL pH
A slide that Vashisth showed recommended keeping soil pH between 5.5 and 6.5 for HLB-affected trees. Other slides explained that with high soil pH, most of the micronutrients bind to the soil and become unavailable. At extremely low soil pH, most of the macro and secondary nutrients become unavailable. The goal is to have the right soil pH at the time when nutrient uptake is expected.

Learn more about how pH affects nutrition.

SOIL-APPLIED VS. FOLIAR NUTRIENTS
Vashisth explained the ways HLB-affected trees uptake nutrients in soil-applied and foliar nutrition programs.

In a soil-applied nutrition program, the plant uptakes nutrients when they are in a solution. When the plant is taking up water, the dissolved mineral nutrients get taken up by the plant and distributed throughout the canopy.

In a foliar nutrition program, thick leaf cuticles limit the nutrient uptake, and a significant amount of foliar spray washes away to the soil. Before HLB, trees had massive feeder root systems and could easily take up washed off nutrients, but HLB-affected trees have few feeder roots and may not be effective in nutrient uptake.

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