A very common and well known disease on roses. the black spots with yellow fringes will spread readily and quickly over the plant. Premature leaf fall may occur. Black Spot becomes visible from July through to August with heavy infections spreading to leaf buds and later to the stems which then die back. Premature leaf drop will occur.
Cultural measures: Remove and destroy fallen infected leaves. Encouraged by a shortage of potash and warm, wet summer weather. Feed with a plant food high in Potassium such as Toprose. Consider growing rose varieties that have been bred to show resistance to black spot.