April 2020The objectives for this proposal are 1) Conduct field trials of new products and fungicide programs for PFD management as well as validation trials for the Citrus Advisory System (CAS); 2) Investigate the reasons for the movement of Postbloom fruit drop (PFD) to new areas and recent major outbreaks; 3) Evaluate methods for initial inoculum reduction on leaves so that early fungicide applications could be more effective and identify the constituents of the flower extracts using omics techniques. We were not able to conduct the trials we had started to plan in January because of the work stopage due to COVID-19. The plots were flagged and we were waiting for the major bloom to open. The shutdown occurred at a particularly sensitive time for the trial just as bloom was starting to open. As a consequence, I have moved my technical employees from this grant at this time because we were not able to acheive our objective. I plan to apply for a no cost extension to be able to do the trials we had planned for the spring of 2020. We did monitor the weather during the shut down and despite several PFD infections periods prior to bloom, no infection periods were predicted during bloom in 2020. Despite obtaining interesting data in the wind tunnel trials, we failed to obtain enough flowers to study the dispersal of C. acutatum from infected flowers. It would be very interesting to better understand the dispersal of conidia produced during this life stage of the pathogen, since it is the most important for inoculum production and PFD epidemics. We were in contact with our USDA collaborators responsible for the wind tunnel in the USDA laboratory in Fort Pierce. We were coordinating with their team to start the trials assessing the potential of dispersal of C. acutatum at the beginning of March to initiate the flower inoculations. However, also due to the COVID-19 pandemic, we were unable to do the trials. Their station has closed before ours and we lost contact. We plan to carry the trials out by the end of this year, if sufficient early bloom occurs. During the 2020 season, we set up two field trials in commercial fields in Florida for the Citrus Advisory System validation trials. They were both located in Ft. Meade, in two different blocks within the same commercial operation. One weekly treatment application was applied, but we were unable to continue the trials due to restrictions enforced by the University of Florida regarding travel within the State of Florida during the COVID-19 pandemic. The monitoring of the weather conditions and the model outputs was not interrupted, nonetheless ,but we could not verify events that were conducive for PFD for the area in which the trials were set up. Due to our inability to visit the fields during the pandemic, we could not verify the occurrence of symptoms in the treated areas. The trials assessing the effect of fungicide applications on the secondary conidiation were repeated. We have added an additional inoculum concentration (a higher one) and verified that the fungicide does not hold back conidia production when inoculum levels are high. This is an interesting result that we intend to repeat shortly. The effect of floral extracts of different floral stages has also been assessed in preliminary trials. We have verified that extracts should be filter sterilized prior to the experiments and that a concentration of 1:100 is the ideal one to conduct our trials and avoid saprophyte proliferation. We will be continuting these experiments as soon as permission is granted from the University of Florida. Flowers of different floral stages were collected and delivered to Dr. Yu Wang’s program so a new set of floral extracts are obtained and the experiments repeated. We will analyze if the pattern of the composition of the extracts holds the same proportion of sugars we verified last year. We will also repeat the experiments with the conidia to check if the pattern we are currently observing holds the same. The different stage flowers were freeze dried and will be extracted as soon as permission is granted by the University of Florida and the new flower extracts analyzed for their constituents We were unable to acheive our field portions of the project as planned due to the shut down and travel ban. These were extenuating circumstances and we hope to be able to receive a no cost extension so we can undertake the objectives next season. Accordingly, I have removed my technical staff from the project as the are unable to work on the project as had been anticipated.