Foliar phosphate fertilization: a simple, inexpensive, and unregulated approach tto control HLB 

Foliar phosphate fertilization: a simple, inexpensive, and unregulated approach tto control HLB o

Report Date: 07/25/2019
Project: 18-024   Year: 2019
Category: Horticultural & Management
Author: Eric Triplett
Sponsor: Citrus Research and Development Foundation

Our team meets every two weeks to discuss progress on this project. We have both greenhouse and field projects in progress.

In Gainesville, a greenhouse experiment is in progress to assess the effect of phosphate fertilization on citrate levels in phloem. In one treatment, we are spraying 2mM potassium phosphate at pH 6.5 on Valencia leaves. In another treament, we provide 2mM calcium phosphate at pH 6.5 to Valencia roots. The idea is that the plants fed calcium phosphate to roots will need to acidify the soil matrix with citrate in order to solubilize the phosphate and make it available. If we spray the leaves with potassium phosphate, no solubilization of phosphate will be required.
Samples from this experiment will be given to Nabil Killiny soon for citrate analysis in phloem.

At Lake Alfred, Nabil Killiny has extablished a terrific greenhouse experiment. He has grafted seedling to infect plants with CLas. He is supplying the plants with the two sources of phosphate as described above. In five months or so, we will assess CLas titer and examine HLB symptoms with the hopre that foliar potassium phosphate fertilization reduces titer and HLB symptoms while the root fertilization with calcium phosphate increases CLas titer and HLB sympotoms.

Meanwhile, the Polk Conty field trial was established and the first sampling is done. The field trials are led by Christopher Vincent. Nian Wang’s group is helping with sampling and the determination of CLas titer. These plants will be sprayed with foliar phosphate for the first time this week.

We have struggled to obtain a field site for this work in the flatlands region. After being unable to have a field trial with Southern Gardens and with a grower in the Indian River area, Dr. Vincent has found a site at the Southwest Florida REC in Immokolee. The experimental plots at that site will be et up next week. Initial sampling and the first spray will be done shortly there after.

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