Enhancement of postbloom fruit drop control measures

Enhancement of postbloom fruit drop control measures

Report Date: 08/30/2019
Project: 16-010C   Year: 2019
Category: Horticultural & Management
Author: Megan Dewdney
Sponsor: Citrus Research and Development Foundation

August 2019 The objectives for this proposal are 1) Conduct ground and aerial applications of fungicides to determine the efficacy and economics of fungicide treatments; 2) Determine if Luna Sensation has enough systemic activity to protect flowers from before they fully develop and open; 3) Determine if the period flowering of trees affected by huanglongbing can be narrowed to eliminate the offseason bloom that contributes to the PFD inoculum increase in groves. Field trials were conducted each year to test new compounds and try new programs with existing compounds.  Unfortunately, in all years but 2016, there was minimal PFD which did not allow for great confidence in the trial results We tried three different methods to investigate the question of Luna Sensation and did not come to a satisfactory answer.  The first year, the experimental approach was flawed and the remaining years, there was insufficient disease to be able to generate an answer. We tried to induce flowering in the greenhouse but failed. Three years of PGR field trials were undertaken and it was found that GA does compress the flowering period but did not reduce yeild when applied once a month from September to December.  It also appears to increase the amount of force needed to remove fruit from trees and reduce fruit drop. The Citrus Advisory Scheduler was developed based on a Brazilian model.  It was modified and optimized for the Floridian situation.  It brings data in from the FAWN system and will allow growers to monitor their risk for PFD.  It also has a log in so growers can get alerts on their phones or e-mail systems. We did 4 years of validation trials for the Citrus Advisory Scheduler.  We determined that the system is very reliable when indicating there is low risk for a PFD infection event.  Unfortunately, there was limited disease during this program and we were unable to evaluate how well it worked when predicting moderate or high risk of PFD infection.  


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