Temporal dispersal of brown and orange rust spores of sugarcane in Florida

Brown rust (caused by Puccinia melanocephala) and orange rust (caused by P. kuehnii) are two economically important fungal diseases of sugarcane. Temporal dispersal of air-borne spores of these two diseases was determined in 2014-2015 in six different locations of the Everglades Agricultural Area (EAA). Real time qPCR assays specific to each pathogen were used to quantify the number of spores captured twice a week on glass slides using wind vane passive traps. Rust spore counts varied according to location and sampling week but spores of P. melanocephala and P. kuehnii were captured every month in at least one location. Data from all locations combined, the highest amounts of brown rust spores were collected from April to June in 2014, and in April, July, and August 2015. The highest counts of orange rust spores were obtained in June-July 2014 and 2015, in November 2014, and in November-December 2015. Rust inoculum appeared to be produced all year long in the EAA but atmospheric spore concentrations varied for each disease throughout the crop season. The number of spores collected per month was higher for P. kuehnii than for P. melanocephala during 9 and 11 of 12 months in 2014 and 2015, respectively, suggesting that the orange rust pathogen may have a higher sporulation capacity than the brown rust pathogen. Temporal variation data of spore dispersal could be used for development of forecasting models to predict sugarcane rust epidemics in Florida