Answer: Black spot thrives in humid, warm conditions, which aren't too common in the arid Southwest except during monsoon season. It sounds as if you are doing things right in regards to watering. We normally recommend being very careful with watering practices, do not water in the evening, water early in the day so no moisture sits for very long on the foliage. Drip of course alleviates this problem. The best way to prevent it is to clean up and destroy leaf drop and prunings, which causes reinfection, and use a dormant spray that includes lime sulfur. Fungal diseases are usually easier to prevent than to treat. A dormant spray smothers insect eggs and disease organisms before they get started. Apply the spray right after you prune in late winter. Other remedies include neem oil, and the fungicide triforine. You might also want to take a sample of the leaves if it reappears to your County Cooperative Extension office for positive identification. They are at 1510 Menaul NW, ABQ, 505-243-1386.
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