Will Black Spot Fungus Kill Roses?

The fungus Diplocarpon rosae can cause discoloration on the leaves and canes of your rosebush, along with faded colors in rose blooms. It can also make it less likely your rose will survive the winter.

Symptoms

• Black spot fungus first appears on the upper side of a rose's lower leaves. It causes round black spots with fringed edges. Infected leaves soon fall off, leaving the rose with only a few new leaves left. This damage weakens the rose and the plant can die over the winter, according to the Ohio State University Extension.

Control

• You can keep black spot fungus from killing your roses by pruning infected leaves and removing all dropped leaves promptly. During dry weather, apply a fungicide to the rose's leaves every week or so. During the rainy season or during periods of rapid growth, you could need to apply the fungicide twice a week, according to the University of Minnesota Extension.

Considerations

• You can help prevent black spot fungus by planting roses in sunny areas where they will not be subjected to splashing water, because splashing water can spread the fungus. The fungus can survive the winter hiding in fallen leaves, so be sure to rake them up and remove them.