The Citrus Research and Development Foundation (CRDF) recently issued a report describing some of its projects testing the injection of oxytetracycline (OTC) into trees as an HLB treatment.
1. Lukasz Stelinski and Kirsten Pelz-Stelinski, both of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), are measuring the impact of OTC injection on the Asian citrus psyllid (ACP) feeding on trees. The hope is that the ACP will consume enough OTC that it kills the Candidatus Liberibacter asiaticus (CLas) in its gut, which would prevent the spread of CLas when the ACP feeds on other trees.
2. Ute Albrecht with UF/IFAS is testing one of the approved OTC injectable products at different dosages. One treatment is at 75% each year for two years, one is at 50% each year for two years, and one is at 150% for just one year. If less of the product can be used and the same result is realized, it would cut the cost of the treatment.
3. John Curtis of Better Crops LLC is evaluating the impact on root growth from OTC. It stands to reason that roots will grow if less CLas is in the tree, but this is a trial that will attempt to quantify response.
4. Curtis is also testing to see if there is a difference between trees injected with OTC and those injected with OTC and treated with gibberellic acid and 2,4-D.
5. CRDF is funding work which experiments with injecting OTC in different parts of the tree. Insertion just below or above the bud union is how growers are applying product and is likely the best method. But if we can quantify movement throughout the tree from insertions in larger branches, it could be easier and less costly for growers.
6. Following grower concerns expressed to CRDF, Henry Yonce of Biotech Agriculture USA and Swadesh Santra of University of Central Florida teamed up to test how long OTC stays viable in the tank (up to three days) after being mixed according to label instructions, and whether there is a chemical, biological or physical change to the solution.
7. Yonce is doing a side-by-side test of trees injected with OTC and those not injected.
8. In 2015, CRDF planted three rootstock trials. The trees are now eight years old, so UF/IFAS’ Albrecht is injecting those trees, leaving untreated trees in the middle of each plot as controls. Each plot had equal injections in the rootstock and the scion, so we will see if there is a difference. With the trees coming into their most productive years, this will be a project that should answer the question of whether there is a difference between an insertion in the rootstock and one in the scion.
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