CLS symptoms include circular leaf spots scattered on the leaves near the base of the plant. The center of these spots on bigleaf hydrangea turns tan or light gray and surrounded by a purple halo. Premature leaf drop can lead to loss of plant vigor and setting of the flower bud. Mostly an issue in the landscape than in the greenhouse.
The appearance of the spots on the upper side of the big leaf hydrangea leaves have a frogeye pattern. These spots are however angular in oakleaf hydrangea. The symptoms can also be noticed on the underside of the leaves.
Fallen diseased leaves serve as the primary source of spores of C. hydrangeae.The spores are spread to lower healthy leaves by splashing water. Frequent summer rains are conducive for disease spread.