Dynamics of coffee leaf rust (Hemileia vastatrix) in Puerto Rico: associations with season, cultivar, altitude, and hyperparasites

Yobana A Mariño¹Diana Buitrago¹Luz M Serrato-Díaz^2*Emily Almonte-Javier¹Sebastián Negrón¹Paul Bayman¹

• ¹University of Puerto Rico, San Juan, Puerto Rico
• ²USDA-ARS Tropical Agriculture Research Station, Mayagüez, Puerto Rico

Coffee leaf rust (CLR), caused by the fungus Hemileia vastatrix, is the most serious disease of coffee worldwide. CLR has been present in Puerto Rico since 1989, yet its incidence and severity have not been reported. We surveyed CLR incidence and severity for three years in fifteen sites and tested associations with environmental variables. CLR hyperparasites were also surveyed. CLR incidence ranged from 0% to 100% and severity from 0% to 60%. Both incidence and severity increased during the dry season following harvest. Environmental variables were important drivers for CLR and its hyperparasites in the field. The incidence and severity of both CLR and its hyperparasites were negatively correlated with temperature and rainfall. While CLR was positively correlated with mean relative humidity and leaf wetness, hyperparasites showed a negative correlation with both minimum and maximum relative humidity. CLR-susceptible cultivars had significantly more CLR than resistant cultivars, but the resistant cultivars also had CLR damage and followed the same seasonal pattern. The resistant cultivar with the most CLR damage was Marsellesa, widely planted to replace CLR-susceptible cultivars lost to Hurricanes Irma and Maria in 2017. CLR incidence and severity both increased significantly with altitude (range 400-951 m). Hyperparasite incidence and severity followed the same seasonal pattern as CLR. Some of the patterns reported here are like previous studies in other areas. They form a baseline for management decisions on cultivars and control, and a point of comparison for future studies.