Flowering Crab Problem - Ask Extension
I have a 45 year old large flowering crab tree. I have had it sprayed in the past for apple scab (I think). The last two years I have sprayed it myse...
Knowledgebase
Flowering Crab Problem #872369
Asked June 10, 2024, 10:22 AM EDT
I have a 45 year old large flowering crab tree. I have had it sprayed in the past for apple scab (I think). The last two years I have sprayed it myself with the Orchard Spray pictured. This year I sprayed it before it bloomed. The tree bloomed normally. Now the leaves have started dying. Do you know what I can do about this? Do you think the whole tree will die?
Thanks,
Sue Abrahamson
Hennepin County Minnesota
Expert Response
Growing conditions in the Twin Cities area differ greatly from last year. Abundant rain is mostly a blessing in that respect, but wet conditions are conducive to the spread of scab, fire blight and other apple tree diseases.
We can't be sure what's affecting the tree by viewing the photos. However, based upon what we can see, it's possible that more than one factor accounts for the leaf drop.
Some of the leaves have lesions that resemble scab. However, we also see what appear to be dead, twisted, leaf clusters typical of fire blight.
Although the sulfur-based orchard spray you used is probably labeled for use to prevent scab, the following University of Minnesota publication has this to say about that: Sulfur-based sprays "may burn plant tissue, especially in times of high heat".
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
So, it's possible that all three of these factors may be in play.
In most cases crabapple trees defoliated by scab recover and even bloom normally the following spring.
If fire blight is present, the tree's health may be in jeopardy. The following publication discusses fire blight. You may be able to use the information there to determine whether fire blight is present and decide what to do about it if it is.
https://extension.umn.edu/plant-diseases/fire-blight
We can't be sure what's affecting the tree by viewing the photos. However, based upon what we can see, it's possible that more than one factor accounts for the leaf drop.
Some of the leaves have lesions that resemble scab. However, we also see what appear to be dead, twisted, leaf clusters typical of fire blight.
Although the sulfur-based orchard spray you used is probably labeled for use to prevent scab, the following University of Minnesota publication has this to say about that: Sulfur-based sprays "may burn plant tissue, especially in times of high heat".
https://extension.umn.edu/plant-diseases/apple-scab#fungicides-to-protect-ornamental-crabapples-from-apple-scab-3652960
So, it's possible that all three of these factors may be in play.
In most cases crabapple trees defoliated by scab recover and even bloom normally the following spring.
If fire blight is present, the tree's health may be in jeopardy. The following publication discusses fire blight. You may be able to use the information there to determine whether fire blight is present and decide what to do about it if it is.
https://extension.umn.edu/plant-diseases/fire-blight
