October 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. Nothing further was conducted on the fungicide or CAS validation field trials. We were unable to apply our fungicides during bloom because of the COVID-19 shutdown. We plan to start the planning and set up in the next quarter for these trials in 2021 if we are granted our requested no cost extension.Further work on leaf wetness has been done to investigate how well individual sensors work for leaf wetness duration estimation. This will be presented as a oral presentation at the virtual FSHS meeting in 2020 along with a written document. It was found that the simpler-to-use Deccagon sensors would be less sensitive for leaf wetness duration estimation compared to Campbell sensors in FAWN stations but that they are adequate for risk determination. The risk mapping has been continuing and we are gathering Postbloom fruit drop risks for major citrus producing locations in Florida and intend to analyze data shortly.We are currently setting up several trials assessing the effect of floral extracts on important metabolic processes of the life cycle of C. acutatum. Dr. Wang’s lab has prepared floral extracts using flowers at different developmental stages – pinhead (small white floral buds), popcorn (expanded floral buds), and open flowers. All three extracts from the different floral stages greatly stimulated pathogen development. Based on previous studies, we anticipated that the sugar content on the extracts was responsible for stimulating the pathogen to become active and cause disease. Therefore, the sugar composition of the floral extracts was analyzed and model solutions containing the same proportion of different sugars were prepared. In vitro assays tested the effect of the sugar solutions and compared them to the floral extracts. Although the sugar solutions stimulated the pathogen, the stimulus was not nearly as large as that posed by the floral extracts. Our team is waiting forthe flowering period to collect more flower samples and perform a bioactivity-guided fractionation and identification of the flower extracts. Such fractionation aims to precisely identify the compound or compounds of flowers responsible for pathogen stimulation. Citrus leaves (young and mature leaves from Valencia trees) were also collected and provided to Dr. Wang’s lab so an extract could be obtained and tested in vitro to check for pathogen stimulation. Any common compounds will not be included in our flower extract evaluation if no stimulation is observed, as we expect based on what is observed in the field. We are in conversation with the USDA to recommence work in their wind tunnel to conduct the experiment with conidia on flowers for the final comparison. However, it is not clear when the USDA will reopen their facilities. We hope it will be soon. We were unable to acheive our field or wind tunnel portions of the project as planned due to the shut down and travel ban. These were extenuating circumstances and we have requested a no cost extension so we can undertake the objectives next season. Accordingly, I have removed my technical staff from the project as they are unable to work on the project as had been anticipated.