| Anthracnose | ashes, oaks, maples, basswood, dogwoods | A fungal disease causing discolouration of leaves and possibly defoliation. Anthracnose does not cause permanent damage, but can weaken the tree. | do not overhead water, i.e. water with sprinkler; ensure adequate air circulation around leaves and stems; plant in well-drained soil and mulch and water in dry conditions | rake up leaves and prune out dead and dying branches, a source for re-infection in the following season and remove from site; can be included with city-collected yard waste |
| Blight Diseases | serviceberry, basswood, pines | A fungal or bacterial disease affecting flowers, leaves, and shoots causing young growth to turn black or brown and curl up. | avoid overfeeding and severe pruning | in summer, remove limbs, cutting well outside infected area (6-12) and dispose |
| | | | for severly infected trees, contact a certified arborist |
| Canker | cherries, ashes, redbud, white pine, oaks, maples, basswood, spruce | Fungal diseases where the infected wood swells and cracks open. A thickened callus may form around the infected area. Can cause branch dieback. | avoid wounding trees | remove cankerous tissue in dry weather and prune away infected areas |
| | | protect trunks from sunscald | make sure to clean tools between cuts to prevent spread of disease |
| | | prevent drought and flooding | |
| Downey Mildew | viburnums | A fungal disease visible by a lightly coloured growth on underside of leaf and angular spots of dead tissue between leaf veins | avoid overhead irrigation in spring | rake leaves in autumn and remove from site |
| Galls | maples, oaks, cherries, basswood | Certain bacteria, fungi, insects, and viruses induce the development of swollen plant tissue. Severely infected leaves are distorted. | attract predatory birds and other beneficial organisms to your yard - these will depend on which insect or mite is causing the problem | the majority of galls are cosmetic in nature and do not cause significant damage to the tree - tolerate them, don't spray |
| | | | determine which type of gall to determine action |
| | | | for oaks and pines, prune out and destroy galls when they occur |
| Needlecast | pines and spruces | A fungal disease of conifers. Most trees recover the following year, producing new, healthy growth. | plant trees where there is good air circulation | prune off damaged tips |
| | | protect young trees from winter frost and winds | rake up dropped needles and remove from site |
| Powdery Mildew | hackberry, serviceberry, viburnums, oaks, maples, tulip tree | A fungal disease which leaves a powdery covering on infected leaves. Many fungi cause this disease most can only infect one or a few plant species. | provide good soil drainage and air circulation | spray with garlic spray |
| | | | remove plant parts that show symptoms and dispose |
| Sooty Mold | tulip tree, nannyberry, maple, alder, birch, dogwood, basswood | This is not a pathogen, but merely fungal growth on honeydew secreted by aphids higher up on tree which has dripped onto the lower leaves | | control aphids with mild soap spray |
| Wilt | maples, redbud, oaks | A fungal tree disease which plugs the water conducting vessels and greatly reduces the flow of water up the stem of the tree. | provide adequate watering and composting | prune out diseased branches |
| | | do not plant another tree of same species in the infected soil | feed diseased tree with a high nitrogen fertilizer like bonemeal |
| | | | where there are multiple trees of same species in close proximity and one is infected, contact a certified arborist to control spread of disease |
| Fire Blight | serviceberry | Sudden wilting an ddeath of branch tips. Bark appears shrivelled and blossoms wilt, turn black, and hang on the twig. | Do not fertilize with high nitrogen fertilizer | prune out and remove infected woods |
| | | | disinfect tools between cuts |
| Leaf Spot | serviceberry, tulip tree, ashes, hackberry | General term for fungal diseases caused by a number of different pathogens for which spotting on leaves is the predominate symptom. Anthranose and tar spot are examples of leaf spot disease. | do not overhead water - use a hose, not a sprinkler; reduce humidity between plants by providing adequate space between plants and by pruning lower branches | remove and dispose of spotted leaves on plants that have fallen |
| | | reduce humidity between plants by providing adequate space between plants and by pruning lower branches | |
| | | use mulch under trees | |
| Leaf Blister | oaks | A fungal disease of oaks that appears as yellow-white blisters up to 1/2"" in diameter on upper leaf surface, with corresponding yellowish brown depression on leaf undersides. Numerous spots will cause leaf to fall prematurely, but does not seriously affect tree health. | maintain plant vigour | collect fallen leaves and remove from site |
| Rust Diseases | ashes, oaks, serviceberries, pines | A fungal disease that causes leaves to become distorte and twigs to swell. Powdery yellow-orange spots may be present on undersides of leaves. Life cycle of fungus requires evergreens as alternative host. | do not plant both hosts near each other, i.e. do not plant serviceberry near juniper | keep tree well watered and increase soil organic matter |
| | | | rake up leaves and fallen branches in fall and remove from site |
| | | | hand pick or prune out galls on evergreens before they swell |
