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Anthracnose (fungus)  |
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Large, irregular brown spots mostly along leaf margins. In rainy seasons, when the disease is most severe, leaves drop prematurely |
Refer to the PDC Fact Sheet "Leaf Spot Diseases of Shade Trees and Ornamentals" for more information. Collect and remove fallen leaves. Usually, disease is not serious enough for fungicidal control, except in unusually wet seasons or locations with severely restricted air circulation. Use chlorothalonil, fixed copper compounds, mancozeb (some brands of mancozeb are labeled for white ash only), quaternary ammonium compounds, or thiophanate-methyl. Green ash is relatively resistant. |
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| Decline (various causes) |
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Trees lose large branches over several years and may die. No one cause has been identified. It is probably a complex of insect, disease and environmental problems, such as moisture stress and freeze injury. A close association between ash decline and ash yellows, caused by a phytoplasma, has been reported. |
Follow standard horticultural practices for pruning, fertilizing and watering. If specific insect or disease problems are recognized, appropriately treat each specific problem. |
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| Flower gall (mite) |
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Male flower clusters become enlarged, distorted and woody. May persist on tree one or more years.
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Does not affect tree vigor. See MU publication G 7272 |
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Leaf scorch (various causes) |
Leaf margins brown and dry up when water uptake is less than water need. May be due to drought, a xylem limited bac terium, Verticillium wilt or root diseases associated with decline. Mycophaerella leaf spot may resemble this. For more information, see MU publication G 6881. |
See leaf scorch in General Problems table. Water deeply during dry periods. |
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Mycosphaerella leaf spot (fungus) |
Irregular browning and blotches usually occurring in the summer or fall. |
Refer to the PDC Fact Sheet "Leaf Spot Diseases of Shade Trees and Ornamentals" for more information. In fall, clean up fallen leaves. |
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Plant bug (insect) |
Leaves may be mottled, stippled, distorted or have irregular brown spots. Black excrement may appear on either surface. |
The feeding of these insects has little effect on plant vigor. |
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Verticillium wilt (fungus) |
Leaf scorch, dieback of branches and long-term decline. |
No fungicidal control is possible. Remove severely affected plants. Replant only with resistant species. |
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Yellows (phytoplasma) |
Decline, premature death, witch's broom, suckering from limbs and trunk and leaves and twigs stunted are increased evidence of freeze injury. |
Remove affected trees. Both green and white ash are affected, but green ash often tolerates infecton without progressive decline. |
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| University Outreach and Extension does not endorse commercial products. Follow the label on all pesticides. |
