July 2015 The objectives of this proposal are 1) Determine the base line level of Guignardia citricarpa sensitivity to fungicides registered for disease control in citrus and evaluate new products for efficacy against G. citricarpa in vitro; 2) Conduct and improve implementation of spray trials for efficacy of registered products for citrus and to evaluate novel compounds in the field; 3) Optimize field evaluation of control measures through analysis of the spatiotemporal disease progress utilizing past and current field data of the outbreaks to gain knowledge on the incidence, severity and rate of the epidemic and assess the fungal population to increase the likelihood of successful field research and 4) Evaluate products and treatment conditions for postharvest control of citrus black spot. This quarter we accomplished: Objective 1: Manuscript preparation continues for the DMI fungicides. Assays with SDHI’s are continuing and different media are being evaluated for best functionality. Experiments with Cannonball and Vanguard are continuing. Most of the mycelial tests are complete and spore germination assays are underway. Objective 2: Fungicide trials were initiated in May 2014 and completed March 2015. Thirteen different fungicide regimes utilizing eight materials, both registered and experimental, were evaluated for their effectiveness in suppressing CBS. Fruit were assessed on the tree for the proportion of symptomatic fruit as well as the proportion of symptomatic fruit on the ground. Several fungicides regimes showed significant differences at one or more rating and results from this and previous trials are being used for product label expansion for CBS. Objective 3: Sites were re-mapped in December 2014 to assess changes (trees pulled and/or re-planted) between the 2013-2014 and 2014-2015 citrus seasons. Trees were mapped for the presence or absence of CBS in two �Valencia� groves. Positive trees were defined as having fruit with at least a single hard spot lesion. The hard spot lesion was chosen due to its ease of recognition as a symptom of CBS. Data for CBS were collected from both groves between December 12th 2014 and April 16th 2015. Grove I consisted of 2144 trees (22 rows x 103 tree spaces; 122 spaces open). Eighty trees were positive for CBS (3.7%). Grove II consisted of 4347 trees (36 rows x 127 tree spaces; 225 spaces open). Seventeen percent (739/4347) were positive for CBS. The binomial dispersion index (D), revealed clustering of symptomatic trees for both groves in all quadrant sizes tested. Monte Carlo simulations for the L function in R confirmed CBS aggregation for both groves. Monitoring will continue through the 2015-2016 citrus season. Objective 4: Fruit quality measurements were made on fruit tested with carvacol and thymol. Peel injury was noted with both treatments but especially for thymol.