Posted by mike grzesiak on June 25, 2003 at 19:07:28:
In Reply to: Peach Tree - black spots on leaves posted by romeu on June 20, 2003 at 19:52:53:
: My fairly young white peach tree has developed some black spots on the leaves and it seems to be spreading to a nearby peach tree.
: What should I use and what is this?
This is probably scab. "Peach scab, also known as "freckles", is caused by the fungus Cladosporium carpophilum . Disease symptoms occur on the fruit as small (less than ¼ inch in diameter) velvety dark spots and cracks. In cases of severe infection, spots may join together to form large dark lesions. Leaf infection is usually not observed. Twig infections occur on the current year?s growth and are light brown after30 to 70 days, before later enlarging and becoming dark reddish brown the next season. Spots on the fruit only occur on the outer skin, and eating quality is not affected. Peel fruit to remove all traces of the disease.
Prevention and Treatment: Most varieties are susceptible to scab, although some are more severely affected than others are. Generally, scab is most severe the first year the trees bear fruit, since a large number of twig lesions can develop during the first two growing seasons when no fungicides have been used. Minimize infection by selecting planting sites that are not low-lying. Trees should be properly pruned to allow good air circulation. This helps to promote rapid drying of the leaves, fruit, and twigs.
Periods of rain with temperatures of 65 to 75 ºF are optimal conditions for infection. Fungicides can provide adequate control of this disease if applications are properly timed. If disease control is desired, apply either wettable sulfur (minimum 80% actual sulfur), azoxystrobin or captan. Make five applications after petal fall at 7 to 14 day intervals. Apply all chemicals according to label directions."