Answer: The fungus Entomosporium mespili is responsible for the leaf spot on your Indian hawthorn. It is most active during prolonged periods of cool, wet weather in the spring. Fungal spores overwinter on infected leaves or juvenile shoots. High humidity, cool weather, and splashing water from rain or overhead irrigation provide an ideal environment for disease spread. You can protect your hawthorn by spraying a fungicide at 7-10 day intervals during the spring growth spurt but a fungicide spray will not fix the damage already evident on your hawthorn. Rake up the fallen leaves and remove them from the garden and use a fungicide to protect the newly emerging shoots and leaves.
Best wishes with your hawthorn!
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