Leaf Spot Diseases on Knock Out Roses
The Knock Out rose family, introduced in 2000, are hardy, disease-resistant rose shrubs that measure 4 feet tall and 3 feet wide, according to Texas A&M University's website. However, minor leaf spot diseases are a concern of Knock Out growers. Does this Spark an idea?
-
Cercospora Leaf Spot
-
Caused by the fungus Cercospora beticola, Cercospora leaf spot is a foliar disease of the Rainbow Knock Out. Small purple leaf spots measuring 2 to 4 millimeters in diameter with tan to brown lesions as the disease develops identify an infection, according to the University of Florida website.
Black Spot
-
Black spot, caused by the fungus Dicplocarpon rosae, is a common disease of roses and can infect disease-resistant Knock Outs. Symptoms of infection consist of black spots on the upper side of the rose leaves, yellowing of infected leaves and leaf drop, according to the University of Maine Cooperative Extension. Wet and warm-weather conditions favor infection.
-
Control
-
Cercospora leaf spot rarely causes a severe infection in Knock Out roses; however, fungicidal spray is an effective method of control in the case of severe infections, according to the University of Florida. Fungicides are an effective method of prevention and control for black spot, according to the University of Maine Cooperative Extension website.
-
References
- Texas A&M University AgriLIFE Extension: Knock Out Rose
- University of Florida IFAS Extension: Cercospora Leaf Spot of Rose
- University of Maine Cooperative Extension: Black Spot of Rose
- Alabama Cooperative Extension System: Disease Resistance of Shrub Roses and Early Leaf Shed Seen on Some Knock Out Roses
