December 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. In the large field trial, there was a greater amount of G. citricarpa DNA found in 2015 leaf litter so that while there was more G. mangiferae than G. citricarpa, it was less than 10 times. In 2014, there was no pattern in the number of leaves with Guignardia structures over time in any treatment but in 2015, the % leaves with structures increased until the third collection date and the started to decline. In 2015, the treatment with the least number of leaves with structures was urea over all. In 2015, the pattern of structure formation was consistent across treatments and over all the treatment with the fewest structures was urea. There was greater G. citricarpa DNA in the control whereas for G. mangiferae there was more DNA in the soilset treatment. The bagasse field trials confirmed the laboratory experiments that bagasse increased the leaf decomposition rate compared to nothing or urea. Greater soil moisture also accelerate leaf decomposition. The manuscript preparation is still continuing. Collection of leaf samples from the grove in Immokalee has continued biweekly. Each batch of samples contained 40 samples of 25 leaves collected below 40 trees. Leaves were examined under microscope to check for fructification of Phyllosticta spp. Leaf portions without fructification were discarded and the remainder were immersed in 0.02% tween20 to collect conidia and ascospores. Conidia and ascospores produced in leaf litter were quantified, weather data were collected from FAWN. Data collection is continuing and some of the qPCR data has been processed. In 2014, very little G. citricarpa DNA was found overall while G. mangiferea was high but, substantially more G. citricarpa DNA was detected in the 2015 collections. In Australia, confirmation of the ascospore production results continues. Inoculations of fruit are underway in the field but no symptoms from this year. From the 2014 inoculations, there are some promising crosses that did not form any lesions and no Guignardia citricarpa was isolated. They are repeating the fungicide work to confirm previous results. They are also continuing to sample leaf litter in two groves in Queensland mandarin growing region.