Apple scab on crab apple tree - Ask Extension
Hello,
I'm from Minnesota(Shoreview) and just had an arborist come to look at my crabapple trees that I suspected had apple scab. He confirmed that i...
Knowledgebase
Apple scab on crab apple tree #870834
Asked May 30, 2024, 5:35 PM EDT
Hello,
I'm from Minnesota(Shoreview) and just had an arborist come to look at my crabapple trees that I suspected had apple scab. He confirmed that it had apple scab and might have fireblight as well. He said they could start treatment right away. To my understanding apple scab needs to be treated by fungicide as the leaves are budding and is too late now. Are they trying to take advantage of the situation by pushing a 4 stage spray treatment now(5/30)? I do not recall any issue with the tree last year. The crabapple trees has a beautiful big pink bloom this year in the early spring. Attached is what the tree leaves look like now 5/30. Leaf density less than 50% now.
Ramsey County Minnesota
Expert Response
The arborist is ISA Certified Arborist from Saveatree
This excerpt from a University of Minnesota publication addresses your question:
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
Frequent rain and humidity this spring have created optimum conditions for scab infection. Even trees that are usually scab free have been affected.
Fortunately, affected trees often bloom normally the following year. However, frequent infection weakens them.
"Do not apply fungicides to a diseased tree
Fungicides only protect healthy trees from becoming infected. Once leaf spots appear in the tree, fungicides will not control the disease.
If your tree is already infected with apple scab this year:
- Do not apply fungicides this year.
- Follow the guidelines above to remove fallen leaves at the end of the growing season and prune to open the canopy in winter.
- Consider applying fungicides the following spring if the tree has lost most of its leaves to apple scab for three or more years in a row."
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
Frequent rain and humidity this spring have created optimum conditions for scab infection. Even trees that are usually scab free have been affected.
Fortunately, affected trees often bloom normally the following year. However, frequent infection weakens them.
