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Poster: Biology & Disease Mgmt: Mycology


Progress of severity of brown rust and orange rust during two sugarcane crop seasons in Florida
S. SANJEL (1), M. Hincapie (1), B. Chaulagain (1), J. Comstock (2), R. Raid (1), P. Rott (1) (1) University of Florida, U.S.A.; (2) USDA-ARS, U.S.A.

Brown rust (caused by Puccinia melanocephala) and orange rust (caused by Puccinia kuehnii) are currently the two most damaging fungal diseases of sugarcane in Florida. To determine progress of these two diseases during the crop season, brown rust susceptible cultivar CL90-4725 and orange rust susceptible cultivar CL85-1040 were planted in field experiments at Belle Glade in November 2013 and in November 2014. Intensity of pathogen sporulation and percent rust affected area were assessed on the top visible dewlap leaf (TVD) and the fourth leaf below TVD every two weeks. Brown rust symptoms were mainly observed from mid-March to mid-July in 2014 and from mid-April to mid-August in 2015. Sporulation intensity and leaf damage was highest in May-June 2014 but this period shifted to June-July in 2015. In contrast, orange rust symptoms were observed all year round, but sporulation and percent diseased leaf area peaked from mid-May to early August. Later on, disease severity decreased until October when another significant increase of orange rust occurred until the end of the year. This pattern of orange rust progress was similar during the 2015 and 2016 crop seasons. Overall, disease severity was higher for orange rust than for brown rust and orange rust impacted sugarcane growth for a longer period of time during the crop season. Conducive environmental conditions for disease progress remain to be determined but appear to be broader for orange rust than for brown rust.