Black Spot

Sunday, March 23 2003 @ 01:34 PM

Problem/Symptom Circular black spots 1/4 inch in diameter appear on upper leaf surfaces. Each black spot is surrounded by a yellow halo. As the spots enlarge and coalesce, the entire leaf turns yellow and falls from the plant.

Cause Black Spot. This fungus disease is most common in humid and rainy conditions; the fungus spores germinate in water. Once a plant is infected, the fungus will remain in the canes through the winter and reappear on the next season's growth. VERY common in the Pacific Northwest. Solution There is no chemical cure for infected plants. In the early spring, after an infection, prune the canes back lower than normal to eliminate fungus spores that remain on the canes over winter, and apply a commercial anti-fungal spray before the leaves open. To prevent black spot from infecting new plants, spray with a synthetic chemical fungicide once every 10 days, starting in midspring. If symptoms appear, remove and destroy all infected leaves, including those on the ground. Do not water plants from above; wet leaves are hospitable to germinating spores.

http://www.mygardenpatch.com/20030323133444239.htm