Knowledgebase
Disease on plant leaves. Causing leaves to fall of and plants dying. #884787
Asked September 10, 2024, 4:55 PM EDT
I live in Bath, and have a continuing issue with plants on our yard. More specifically peonies, lilacs and flowers(annuals). My husband and I are both MSU alums, John retired from MSU in 2022 after 41 years there.
The problem is that our beautiful lilac bushes which have lined our property on the road side have lost all its leaves and appears dead or dying. There seems to be some type of disease that has affected most of our flowers, including milkweed. The milkweed stalks got black and brittle and all the leaves fell off. I have since had to cut them all down. It also seems to be even on the weeds in the ground- a white dusty film. I am enclosing some photos.
Would it be possible to arrange for someone to come and look at what is happening here? Thank you for your consideration.
Sincerely,
Arlene
Clinton County Michigan
Expert Response
(I removed your surname to protect your privacy in this public database )
MSU Extension is not staffed to make residential visits.
We have had many questions from all over Michigan this year about lilacs dropping leaves early, brown spots, appearing to be dying, etc. This is due to fungal leaf spots that have run rampant this season due to the wet weather.
Other plants have the same issues, especially when their leaves stand wet overnight. This encourages all sorts of fungal leaf spots to grow.
Here is a response to a client with the same lilac issue as yours, and it describes what you can do.
“Lilacs, and many other plants, shrubs and trees, are all prone to a number of pest issues that can impact their appearance late in summer. One common factor is likely the rainy spring and summer we have had in Michigan. We are seeing a lot of fungal issues on a wide variety of plants this year. Many lilacs and crabapples are losing their leaves right now.
New growth at the tips of the lilacs shows the plant is still live.I suspect this lilac has a number of older dead branches and others that have just lost their leaves for the season due to one or more fungal issues, such as a fungal leaf spot or powdery mildew.
Treating with any fungicide at this time of year is not advised. Make sure you've got good air flow around your lilac if possible and remove all fallen lilac leaves to prevent any further spread of the disease. Hopefully, with a drier spring next year, you will not see much of this issue on your lilac next year.
Click on these links below to read more about these pest issues:
Lamentable Lilac Leaf diseases (purduelandscapereport.org)
In addition to highly likely fungal issues, the lilac could also have some borer damage, as many older lilacs often do.
Here is a link to an article about that pest:
Lilac borer is a pest that may weaken shrubs over time - Gardening in Michigan (msu.edu)
You may want to consider pruning out a portion of the older stems as the article above advises, along with any dead branches. This will also help to create better air circulation through the plant, which can reduce fungal issues. If you want to ensure that you have all the lilac blooms possible, then you should wait to prune the lilac until after it blooms next year. All of next year's flower buds have already formed and pruning now would remove some of them. Also, with this much leaf drop and die-back, you want to wait until the lilac's leaves emerge to determine which sections are actually dead.
Pruning information from the lilac borer article linked above: If your lilac is struggling due to an unknown reason, check near the lower 1-3 feet of the plant for evidence of larvae exit holes to determine if lilac borer is a contributing factor. Moderately affected lilacs can be pruned following the guidelines of renewal pruning. This involves removing a third of older stems to the ground level as well as weakened branches in the first year. Subsequently, continue in years two and three by cutting another third. After a season, the shrub will be reinvigorated with newer, healthier stems. If many new stems emerge, select only a few designated ones to promote larger stems and remove the others.”
Arlene, you can thin your lilacs to improve air circulation. If your irrigation hits the shrubs( and flowers or other plants with fungal problems) be sure to water early in the day so leaves dry quickly in the sun. Rake up and bag as many lilac leaves and other diseased plant material as you can to reduce overwintering fungi.
Your peonies have powdery mildew, a common problem on this plant. Here are some management options for you-https://hnr.k-state.edu/extension/horticulture-resource-center/common-pest-problems/documents/Peony%20Powdery%20Mildew.pdf
https://extension.colostate.edu/topic-areas/yard-garden/powdery-mildews-2-902/
