| DISEASE |
TREE SPECIES AFFECTED |
WHAT IS IT? |
PREVENTION |
CONTROL
|
| 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 |
