Answer: The most common and devastating leaf spot of Indian Hawthorn is known a Entomosporium. It is very difficult to control with sprays.
Your cultural technique of removing infected leaves is a good practice. Keep in mind that most infection occurs in the rainy days of spring and fall, or any other time an extended rainy period occurs. That is when sprays are most critical. Leaves infected at those times later develop the visible spots.
Entomosporium often responds best to a spray schedule of alternating between two different types of fungicides. Your County Extension Office (phone 210-930-3091) can recommend other spray products which may give some control.
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