Directed Research Solicitation: Evaluating different rates of oxytetracycline administered by trunk injection in mature sweet orange trees

Directed Research Solicitation: Evaluating different rates of oxytetracycline administered by trunk injection in mature sweet orange trees

Report Date: 08/15/2024
Project: 23-002   Year: 2024
Category: Horticultural & Management
Author: Ute Albrecht
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them: Objective 1: To compare different rates and annual use patterns of trunk-injected OTC on late-season (Valencia) and early-season (Hamlin) sweet orange tree and their effects on health, yield, and fruit quality over a period of 3 years in a commercial citrus production environment.Year-2 injections were completed in May for the Hamlins and in June for the Valencias. Tree size and canopy volume data were collected.  Leaf samples were collected for CLas analysis.  Obective 2: To compare spring with late summer injections in Valencia orange trees to determine if OTC effects on yield can be enhanced, and the harvest window extended, through timing of injections.Valencia OTC fruit residue analyses were completed. Fruit from trees injected in June 2023 had residues below the allowed 10 ppb regardless of the rate. Fruit from trees injected in September had higher residues, suggesting that trees should not be injected in September. This year’s late summer injections will therefore be conducted in August instead of September.    2. Please state what work is anticipated for next quarter: We are preparing for the Valencia August injections. Leaf sampling will be conducted for CLas analysis. Phytopthora trunk rot has been observed in this location. The rot does not seem to be associated with OTC injections; we will conduct measurements/ratings to document this. 3. Please state budget status (underspend or overspend, and why):The budget is as expected. 


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