Mountain Ash Diseases
Gary W. Moorman, Professor of Plant Pathology
| Disease | Symptoms | Pathogen/Cause | Management |
|---|---|---|---|
| Cytospora canker | Trunks and larger branches have brown sunken cankers, circular or irregular in shape, that gradually enlarge and girdle the wood. Black, pimple-like fruiting structures form on infected bark. Yellow threads of spores ooze out of the fruiting structures during wet weather. | Cytospora | Prune infected limbs well below the canker. Disinfest the pruning tools thoroughly between cuts. Remove severely infected trees. |
| Fire blight | Flower clusters are killed and turn dark brown to black. Dead leaves and aborted flower parts remain on the tree. Long, slightly sunken cankers are seen where the dead wood meets the live wood. In the spring, slime may ooze from the canker if the weather is warm and wet. No fungal fruiting structures are found in the canker. Flower clusters are killed and turn dark brown to black. | Erwinia amylovora | During dormancy when the weather is dry, prune infected branches, cutting at least 4 inches below the base of the canker. Disinfest pruning tools frequently. Use fertilization practices that do not promote excessive succulent growth. Remove root suckers and water sprouts while they are small. Remove unwanted plants that are susceptible to the disease from near cultivated plants. Apply copper hydroxide or copper hydroxide + mancozeb. Sorbus aucuparia and S. intermedia are resistant. |
| Leaf spot | Round to irregular, brown spots form on leaflets. Tiny, black fruiting structures form within older spots. | Phyllosticta | No control is recommended. |
Active Ingredients and Trade Names of the Chemicals
| FRAC Group no. | Risk Level | Class | Active ingredient | REI Restricted Entry Interval | Trade names ((EPA Reg. no.) |
|---|---|---|---|---|---|
| M | 1 | Copper, fixed | copper hydroxide | 48 | Kocide (352-656), Champion (55146-1) |
| Combined products | 1 | ||||
| M + M | mancozeb + copper | Junction Fungicide (1812-360) |
Fungicides and Fungicide Resistance Management - Certain fungicides, usually systemic fungicides, are said to be 'at risk' to the development of resistance if they are used repeatedly. See the Risk Level in the above table (1 = low risk; 3 = high risk). The Fungicide Resistance Action Committee has developed a numbering system in which chemicals with the same FRAC Group number have the same mode of action (See http://www.frac.info/frac/index.htm ). It is recommended that chemicals at high risk be used sparingly and in rotation or mixed with chemicals with different modes of actions (different FRAC number).
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Notice: The user of this information assumes all risks for personal injury or property damage.
Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds.
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