April 2021The 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. The two validation trials for CAS have been laid out in the Fort Mead area and a small amount of disease has been observed on early bloom in at least one site. We hope for at least one positive site. There were 3 weekly applications made and 2 applications according to the PFD-FAD. The fungicide trial had one application made on May 8th after a rain period. There were no triggers for disease this year at the site and this was the most likely infection period. Fruit data should be recorded in June or early July. A manuscript is in preparation for all the years of CAS validation. The majority of analysis for the leaf wetness models is now completed and manuscript preparation is continuing. We compared the output of leaf wetness sensors to combinations of predictive models for accuracy and sensitivity. As for all models, reliability was heavily influenced by the quality of the weather station data. Reasonable accuracy was found for one, three, or four models in combination but with just two models, the predictive capacity was poor. We are in discussions for how this information could be used to improve CAS predictions. We are working on evaluating PFD risks via an analysis for prediction accuracy. So far, we have tested floral extracts of pinhead, popcorn, and open citrus flowers. All floral extracts stimulated Colletotrichum abscissum conidial germination, and stimuli were compared among these treatments. We analyzed the sugar composition of the floral extracts. Then, we prepared sugar solutions with the same sugar concentration and composition to that of the floral extracts. The germination stimulus of the sugar solutions was higher than the water control, but less than the floral extracts. We tested the stimulus posed by leaf extracts prepared with new and old leaves on the pathogen. Leaf extracts were as good as floral extracts in stimulating the pathogen. As leaves are easier to obtain and available year-round, we decided to investigate the leaf extracts further, to pinpoint what portion of it was responsible for the stimulus considering polarity. We found that the highly polar portion of the leaf extract was responsible for the stimulus. An untargeted metabolomic analysis revealed that there are thirteen main components of the high-polarity portion of the leaf extract. These components will be tested soon.We have been in conversation with the USDA and found out that they have only just repaired their wind tunnel and had slightly more access to the facilities. In the mean time, as we were unsure how soon we could use the equipment, we decided to build a similar tunnel at CREC. We have done a complete set of experiments with the new tunnel with inoculated leaves and flowers with and without rain. We are analyzing the data and adding it to what we observed with the USDA wind tunnel. The manuscript is in preparation and we may do a few follow up experiments as questions arise during the analysis