Apple scab on flowering tree or other fungus? - Ask Extension
I have three trees/shrubs being affected by something this spring. I am looking for a second opinion, mostly for what is happening to the flowering t...
Knowledgebase
Apple scab on flowering tree or other fungus? #875843
Asked July 03, 2024, 3:35 PM EDT
I have three trees/shrubs being affected by something this spring. I am looking for a second opinion, mostly for what is happening to the flowering tree which may be a non-fruit producing crab apple. I was told it was suffering from Apple Scab. Can the flowering tree have a secondary problem? The leaf damage looks exactly like the what was happening with the leatherwoods planted near it. Most of that row of leatherwoods has died or is dying. I was told from poor drainage. I also lost 4 white birch trees, I was told from a bug infestation. All of these trees are growing around my patio area. Are they all being affected by seperate things, or is there another underlying problem that should also be looked into.
Rice County Minnesota
Expert Response
So far as the flowering crabapple is concerned, we think you have diagnosed the problem correctly. Conditions this spring have been very conducive to the spread of a fungal disease called apple scab. Even some disease resistant trees that are seldom affected are showing symptoms.
Scab often defoliates susceptible ornamental crabapple trees by midsummer. However, trees so affected usually recover, and even bloom normally the following spring. Still, because frequent defoliation weakens trees, control is sometimes needed.
Go here to learn more about scab and how to manage it:
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
Many kinds of plants are affected by leaf spot diseases, but most of these pathogens are host specific, so they are unlikely to occur on plants of disparate genus and species. For instance, scab (Ventura inaequalis) affects plants in the rose family such as apple, mountain ash, pear and cotoneaster, but it does not affect birch or leatherwood. Leaf spot diseases specific to those plants must be taken into account in this case.
Generally speaking, leaf spot diseases do not kill their host plants. In many cases the leaf spots are mostly cosmetic and of little or no consequence so far as plant health is concerned.
Go here to learn about birch leaf spots:
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/birch/leavesspots.html
https://hyg.ipm.illinois.edu/article.php?id=165
As a rule leatherwood isn't seriously affected by leaf spot disease. Leaf spots shown in the photo can probably be ignored. However, some leaves are exhibiting chlorosis which may be caused by unfavorable growing conditions including saturated soil.
Scab often defoliates susceptible ornamental crabapple trees by midsummer. However, trees so affected usually recover, and even bloom normally the following spring. Still, because frequent defoliation weakens trees, control is sometimes needed.
Go here to learn more about scab and how to manage it:
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
Many kinds of plants are affected by leaf spot diseases, but most of these pathogens are host specific, so they are unlikely to occur on plants of disparate genus and species. For instance, scab (Ventura inaequalis) affects plants in the rose family such as apple, mountain ash, pear and cotoneaster, but it does not affect birch or leatherwood. Leaf spot diseases specific to those plants must be taken into account in this case.
Generally speaking, leaf spot diseases do not kill their host plants. In many cases the leaf spots are mostly cosmetic and of little or no consequence so far as plant health is concerned.
Go here to learn about birch leaf spots:
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/birch/leavesspots.html
https://hyg.ipm.illinois.edu/article.php?id=165
As a rule leatherwood isn't seriously affected by leaf spot disease. Leaf spots shown in the photo can probably be ignored. However, some leaves are exhibiting chlorosis which may be caused by unfavorable growing conditions including saturated soil.
