December 2015 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. The most recent set of twigs inoculated gave inconclusive results. Very few conidia were formed and mostly spermatia were formed. Pycnidia did not form as expected. We are trouble shooting and expect to try again in the near future. 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 are testing ideas for collecting spores in the lab and in the field Two types of disinfectants approved by the Florida Department of Agriculture and Consumer Services/Citrus Health Response Program (FDACS/CHRP) were tested for their effect on spore germination in Phyllosticta citricarpa. These disinfectants are quaternary ammonium and sodium hypochlorite. All of the FDACS/CHRP approved quaternary ammonium products contained the same active ingredients in the same concentrations. Therefore two representatives of the approved products were tested. Our preliminary tests for quarternary ammonium indicated that spore germination was reduced to zero at rates as low as 5 ppm. In our study treatments used are: 20, 10, 5.0, 2.5, 1.0, 0.1, and 0 ppm. Preliminary tests with bleach indicated that spore germination was reduced to almost zero at a concentration of 82.5 ppm. Concentrations being evaluated are: 8250 ppm, 825 ppm, 82.5 ppm 8.25 ppm and 0.825 ppm. Trials for both products are currently in process and each product has been tested at least once on five different P. citricarpa isolates. Testing is done using three psuedo-replications per treatment and all treatments will be repeated twice.