Our trees always have some level of fungal leaf spot but whenever we have a rainy cool spring the leafspot diseases increase dramatically. The good news is that even though these diseases look severe they do not do much damage to the trees BUT it is essential that the trees are kept watered on a consistent basis. 1″ of irrigation per week is usually sufficient to maintain soil moisture for the trees. Above 95 degrees increase irrigation to 2″ per week. An application of a moisture manager product (we do provide this service) greatly improves the effectiveness of irrigation and rainfall by allowing the water to move into the soil and and then remain in the root zone. Large trees use huge amounts of water so consistent irrigation or rainfall is essential for maintaining tree health.
Here is cercospora leafspot on white oak.
Cercospora leafspot on beech
Oak leaf blister on water oak.
