September 2017 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. The samples that were previously incubated and dried are now ready for the DNA extraction process. 480 of the 960 samples were processed by removing the bark and homogenizing the tissue using liquid nitrogen and bead beating. The DNA was recovered using the MioBio PowerSoil kit. Another 1,536 samples were processed for incubation. This includes tagging, weighing, measuring midpoint diameter, and recovery and quantification of spore suspension from rinsate. Spore suspension was taken from 672 samples before the incubation period. The spore suspension was quantified and stored at -20�C. An additional 1,152 samples were taken from the field in Immokalee, FL. Our controlled study is schedule to begin in early October and preparations for this large project have already begun. This project will analyze the impact of relative humidity and temperature on growth and dissemination of Phyllosticta citricarpa. A postdoc was hired in September and has started to confirm that the inoculation techniques and containers with the salt solutions will work adequately to move the leaf litter section forward. Work on the effect of FDACS recommended disinfectants (200 ppm bleach or 2000 ppm quaternary ammonium) on conidia germination was conducted. Effective concentrations to inhibit either 50% or 90% of conidia germination for 2 quat products, Canker Solve and C-Quat, and bleach were found to be well below 5 ppm for all products. Bleach was about ten times more effective but is not as stable as quat. The disinfectants have been preliminarily evaluated in the presence of finely ground plant debris (twigs and leaves as would be found on mowers or hedgers). Testing of sodium hypochlorite was conducted during this quarter and is almost complete. Results show that at the lowest ratio of disinfectant to debris (100�l treatment), 1500 ppm a.i. was required to reduce spore germination to zero. This is notably higher than the recommended rate of 200 ppm. Efficacy of sodium hypochlorite is significantly reduced by the presence of debris and, in fact, is not recommended by CHRP for use on dirty equipment. Results of our work demonstrate that the presence of debris significantly reduces the efficacy of disinfectant, but this can be mitigated by using a large volume, relative to the amount of debris. Therefore, the results of this study illustrate that when decontaminating equipment with disinfectant, it should be applied to the point of run-off, rather than lightly sprayed on.