Physiological leaf spot

Leaf spots develop from weather stress, nutrition imbalance, or air pollutants rather than from disease pathogens causing infection. No disease control is needed since this is a physiological condition reflecting environmental stress on the plant. Address underlying stress by improving drainage, adjusting fertilizer based on soil test results, or reducing pollution exposure.

Leaf spot and blotch diseases are primarily cosmetic on established plants, though repeated years of heavy infection can weaken them. Rake up and remove fallen leaves to reduce the spore load going into the next season. Avoid overhead watering that splashes spores from the ground onto lower leaves. If the problem is severe, protective fungicide sprays during spring leaf emergence can help, but sanitation does more than chemistry for most leaf spots.