Septoria Leaf Spot on Dogwood Plant Pathology Septoria Leaf Spot on Dogwood Dogwoods are susceptible to a number of fungal leaf spot diseases. Red and yellow twigged dogwoods are particularly susceptible. Most of the dogwood samples arriving in the Plant Disease Clinic have been showing Septoria leaf spot. This disease typically causes angular, grayish spots with a dark purple or reddish border.
Symptoms usually occur first on lower leaves.
As with many of the fungal leaf spot diseases, wet spring weather favors their development. Diseased leaves should be raked and removed to prevent overwintering of the fungus. Prune out any dead branches. Improve air circulation around the foliage if possible. Mulch and water as needed to improve plant vigor.