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Discolored leaves #877184

Asked July 14, 2024, 5:17 PM EDT

My lilacs look awful with dry brown leaves. Nearby are hollyhocks that also are looking diseased. What is this? Same thing? I’m concerned about 4 new trees I planted nearby this year. 3 northstar cherries and a crabapple. Don’t want them getting sick. Thanks.

Ramsey County Minnesota

Expert Response

It appears your lilac may be experiencing either a response to previous years of drought or a bacterial blight. Bacterial blight can occur when there is lack of circulation and moist conditions. I would recommend removal of the branch areas with the declining leaves. Also take care to rake up fallen leaves and twigs and dispose of in the trash. In your photos it does look like the branches are tight and could benefit from pruning to allow air flow throughout the tree. I have put a link below to leaf spot disease and a video that instructs on pruning. With clean up and pruning your lilac will likely be healthier in the future.
 
It is not likely your newly planted fruit trees will have the issue as your lilac.

In addition, your hollyhock likely has rust. This is evident in the photo with the orange, dust-like substance on the leaves. https://extension.umn.edu/plant-diseases/rust-flower-garden Rust must be treated in its very early stages. Once established it is not treatable. When the plant is done growing clean up all debris and throw in trash. 
Leaf Spot Diseases
https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs#leaf-spots-and-shoot-blight-or-canker-1156510
How to Prune a Lilac
https://video.maine.edu/media/How+to+Prune+a+Lilac+Bush/1_1w8x1rwv
Amy J. Extension Master Gardener - HC Replied July 14, 2024, 11:08 PM EDT
Thanks!

On Sun, Jul 14, 2024 at 10:08 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied July 14, 2024, 11:15 PM EDT
Hi.  Thanks for the earlier help.  Now on the other side of the house my smoke bush is looking awful.  I did trim it minimally for a crew putting in an AC a few weeks ago but otherwise it went from looking great to this (attached).
Any ideas?
Thanks.
Dave McKenna
image
image

On Sun, Jul 14, 2024 at 4:17 PM Ask Extension <<personal data hidden>> wrote:

Dear David,

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YOUR QUESTION #0147102:

Discolored leaves

My lilacs look awful with dry brown leaves. Nearby are hollyhocks that also are looking diseased. What is this? Same thing? I’m concerned about 4 new trees I planted nearby this year. 3 northstar cherries and a crabapple. Don’t want them getting sick. Thanks.

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The Question Asker Replied July 21, 2024, 7:26 PM EDT
Drought or verticillium wilt are two main causes of declining leaves on shrubs. While we have had adequate rainfall this year we did experience drought conditions the previous three years. Supplemental watering, at 1"/week would have been needed to maintain a healthy shrub.

Verticillium wilt is caused by a fungus. It impacts branches by inhibiting the ability for moisture to flow throughout the shrub/tree. Testing in your branches is the best way to determine if the shrub has verticillium wilt. Below is a link with information about this fungus as well as information about the plant disease testing. 

Verticillium Wilt
https://hort.extension.wisc.edu/articles/verticillium-wilt-of-trees-and-shrubs/
Plant disease clinic
https://pdc.umn.edu/
Amy J. Extension Master Gardener - HC Replied July 24, 2024, 10:40 PM EDT

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