Determining best timing for Brassinosteroid (Brs) application to achieve maximum beneficial effects on citrus tree health and fruit yield and quality

Determining best timing for Brassinosteroid (Brs) application to achieve maximum beneficial effects on citrus tree health and fruit yield and quality

Report Date: 02/15/2024
Project: 22-003   Year: 2024
Category: Horticultural & Management
Author: Fernando Alferez
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them:  The objectives of this project are: 1, To study the effect of Brs on priming immunity on young, newly planted trees. This will allow to know for how long immune response will last after Br application, so we can adjust timing (number of applications).After 1 year (with a monthly application), some trees (around 20%) are still HLB-negative. Denser foliage has consolidated in a denser canopy with less leaf drop in winter. Spring flush in Br treated trees has already started in early February and is highly syncronized, following the trend we observed during Summer and Fall flushes.  This confirms our previous observations  that flushing occurred at the same time in Br-treated trees, and will allow better planification of insecticide sprays. 2, To determine the best time of application (frequency) to achieve maximum protection against pests and disease in newly planted trees. We have started to get data showing that even though immunity is maximum by 30 days, it is still significantly high 60 days after treatment as compared to controls. 3, To determine the effect of Br application on advancing fruit maturation in both Valencia and Hamlin. Treatments started in September on Hamlin. We performed two different sets of treatments: biweekly treatment and only once treatment. Last season, there were no differences between biweekly treatments and only once treatment in terms of yield and quality. This season, we wanted to confirm this. We have been following quality  every 15 days, including internal quality and external color development. We started to see a significant increase in Brix with Br treatment performed in mid-November for Hamlin, just like last year. In this case, we had 9.2 Brix in Br treated fruit as compared to 8.4 in controls at harvest.  Ratio was again greatly increased,15 in Br-treated as compared to 11.8 in controls. External color is also increased. Together this is encouraging, as we are confirming results from last year in Hamlin. Interestingly, we had also a mild 25% increase in total yield at harvest. These trees were harvested in January 12. We started treatments in Valencia on January.  Outreach: -OJ BREAK Jan 17, Lake Alfred.  IPC’s and Brassinosteroids to Prolong Health and Improve Fruit Yield and Quality in Newly Planted Trees Under HLB 2. Please state what work is anticipated for next quarter: We will continue treatments in Valencia until harvest. We will perform juice analisis as we did last year in both Valencia and Hamlin to determine the composition of sugars and acids.    3. Please state budget status (underspend or overspend, and why):  Spending continues on track.  


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