April 2016 The objectives of this proposal are 1) To determine the temperature and relative humidity optima for Guignardia citricarpa pycnidiospore infection and production on citrus twigs, leaf litter, and fruit; 2) To determine the relative potential of Guignardia citricarpa to form pycnidiospores on citrus twigs, leaf litter, and fruit; 3) To determine whether Guignardia citricarpa can survive and reproduce on citrus debris on grove equipment. Experiments to confirm initial relative humidity findings continue. After the inconclusive results of the second experiment, we started a third experiment. We used fresh cultures to ensure better pycnidia performance. It is currently incubating Planning of further experiments is underway. A site has tentatively been found to conduct field experiments of inoculum potential and some preliminary work is underway. We have rebuilt a spore tower and have been testing with Diaporthe citri to ensure everything is working. Twigs from a P. citricarpa infested grove were collected and will be tested soon. Studies were conducted to examine P. citricarpa conidiospore survival under conditions existing in the grove and associated equipment. We found that when spores are maintined on inert surface with free moisture incubation periods of up to 3h do not affect the survival of the pycnidiospores at temperatures of 15-30. Spore survival under these moisture and temperature conditions persisted for at least 48 hours. Above 30�C, we saw a rapid decrease in spore survival. At 40�C spore survival of 1 to 2% was observed at 12 and 24 hours and no spores were able to survive for 48 hours. Similarly, for 50�C spore survival dropped to 1 to 2% by 3h and no spores survived for 12 hours. Spores deposited in free moisture but allowed to dry exhibited very poor survival regardless of temperature treatment. Upon rehydration, no spores survived beyond 3 hours.