Reducing fruit drop by altering hormonal responses within the tree through nutritional and hormonal therapies: a mechanistic affordable approach

Reducing fruit drop by altering hormonal responses within the tree through nutritional and hormonal therapies: a mechanistic affordable approach

Report Date: 05/15/2023
Project: 21-007   Year: 2023
Category: Horticultural & Management
Author: Alferez Fernando
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them:Specific objectives are:1) To determine the right timing for Zn and K treatments to minimize fruit drop.2) To determine effects of GA3 and 2,4D applications on fruit retention when applied at different times during fruit development.3) To develop a strong and proactive outreach program.In objective 1, measurements continued in Valencia, and we started monitoring fruit drop in February weekly, after the last treatments were performed in early January. Harvesting was performed on March 28. Results show an increase in Kg per 3 trees after January application: the combination of Zn and potassium yielded 52,75 Kg per 3 trees, as compared to 24.5 in the controls. Zn and K applied alone did also increase yields but to a lesser extent. Yield were 42 Kg per 3 trees after Zn application and 37,5 after K application in January. Yields after other applications (June and July) did not show any significant effects. All in all, this is coincident with what we obserbed in Hamlin, that only the latest application had a significant effect on yield, as a result of fruit drop reduction at a time when it starts to increase due to competence for resources.In objective 2 main activities in this quarterI were finishing up harvesting in Valencia and analyzing data. Yield was higher when GA and 2,4D where used together as this treatment reduced fruit drop from around 40% to 20%. Results from this first season were presented at the citrus grower institute and available online: https://citrusagents.ifas.ufl.edu/archived-presentations/2023/In objective 3, PI Alferez delivered a talk to the Citrus Advisory Committee on May 2 on effects of Zn and K on fruit drop.Tripti Vashsisth gave a talk at the Citrus Growers Institute on Updates on Giberellic acid studies (see above)2. Please state what work is anticipated for next quarter:We will continue  tree growth and HLB assessment and  will start treatments again in June. We will analyze samples that we collected and process data. This will allow us to design treatments for next season. Several talks at professional (FSHS, ASHS) and grower-oriented (Citrus Expo) meetings are expected.3. Please state budget status (underspend or overspend, and why):Spending continues on track. 


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