July 2015 The objectives of this proposal are 1) to determine if a) leaf litter biodegradation treatments reduce Guignardia spp. pseudothecia and improve control afforded by routine fungicide applications; b) if biodegradation is affected by the current fungicide application practices; and c) whether the biodegradation treatments will affect current citrus best management practices (BMP); 2) to determine the seasonal dynamics of leaf litter inoculum load in varying management regime intensities and how environment affects pseudothecia production in the leaf litter; 3) to test if the resistance to black spot in the leaves and fruit in sour orange is correlated and under simple genetic control through laboratory and field testing of progeny of sour orange crosses in both Florida and Australia. Data was collected for the large field trial and preliminary analysis was begun. The fruit incidence and severity was collected. The manuscript from the experiment to look at the effect of bagasse is still in preparation. Forty leaf litter samples were collected and assayed between January and April 2015 in a Florida grove to obtain a better understanding of the seasonal patterns of spore production in citrus leaf litter. Each sample contained 25 leaves collected from 40 randomly selected trees in a grove near Immokalee in Collier County biweekly. All leaf litter samples were evaluated under the dissecting microscope to assess degradation level. One or more pycnidium and/or pseudothecium from each leaf was examined under the microscope until positive Phyllosticta spp. fructification was identified. Leaves without Phyllosticta spp. fructification were recorded and discarded. Spores were collected by immersing leaf litter in 0.02% Tween 20, and quantification was performed by counting the spores using a haemocytometer. Preliminary weather data were obtained from the Florida Automated Weather Network (FAWN). In Australia, the proportions of the various Phyllosticta fruiting bodies (spermogonia, pycnidia and pseudothecia) were observed by microscopy. The data show a similar pattern to the 2013-14 season, with pycndia dominating at the beginning of the season, then becoming less frequent. Similar peak in pseudothecia production to the 2013-14 season can also be observed, though this peak was smaller and later in 2014-15. In the germplasm inoculation experiments the susceptible controls are starting to show symptoms. The negative controls have not. Sampling will continue for several months. In the parallel microplots for enhanced leaf litter decomposition, it was found that no one treatment over time consistently had the lowest number of fruitifications and all leaves showed similar rates of decomposition. This is similar to what we previously found when examining the rate of decomposition. The amount of water used for fungicides is very high and run-off very common. When the effect of run off was evaluated, there was no improvement for the number of fruiting bodies produced.