Different genotypes or races of M. rosae, i.e., isolates that infect a specific cultivar or group of cultivars have been identified. Certain species of roses and cultivars of old garden roses are considered more resistant to the disease than modern cultivars. Modern roses and especially the popular hybrid teas are not only more susceptible to the disease, but also are considerede high maintenance roses in Florida requiring more attention to disease control, fertilization, and irrigation.