Black Rose Spot

How can I treat the black spots on the upper surface of my rose leaves and canes? (Black Rose Spot)

Symptom(s): 

Small, round spots, ranging in size from 1/16" to 1/2" in diameter, appear on the upper sides of leaves. Leaf tissue adjacent to the spot turns yellow. Whole leaves eventually turn yellow and fall prematurely.

Cause(s): 

Rose black spot, caused by the fungus Diplocarpon rosae, is the most common cause of defoliation of landscape roses in Virginia.  Susceptible landscape roses must be sprayed frequently with fungicides to keep the disease under control. Fortunately for rose growers, some of the newer cultivars and hybrids have resistance to this disease.

Control(s):

A preventative program for black spot should begin in the fall with a thorough sanitation program. Diseased leaves on the ground should be raked and burned or removed. All diseased canes should be pruned back to healthy wood. These practices will reduce the amount of over wintering fungus. During the growing season, overhead irrigation, which prolongs leaf wetness, should be avoided. If plants are overhead irrigated, watering should be done in the morning rather than the afternoon so that leaves dry quickly. Fungicides registered for black spot control should be applied preventatively to susceptible roses starting in spring before the new leaves become spotted.  From this time through frost, the plants should never pass through a rainy period without a protective coating of fungicide on the leaves.  

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