Disease on spirea (I think) - Ask Extension
About half the shrub has died off. We have located two particularly odd spots and are wondering what the disease is and what the remedy might be. The ...
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Disease on spirea (I think) #395204
Asked April 22, 2017, 9:39 AM EDT
About half the shrub has died off. We have located two particularly odd spots and are wondering what the disease is and what the remedy might be. The white one seems to be a mould/mildew. But the other is more strange. Below are photos.
These plants are in landscaped areas at Medina Ridge Condominium in Medina, MN.
Please answer to Lois Marek at <personal data hidden>
Thank you.
Hennepin County Minnesota
Expert Response
Hi and thank you for sending good photos. It does appear to be fungus but some scale insects can also look similar.
I recommend cutting out any branches that look infected and keeping an eye on it. If you see this return in the summer months then it can be treated with horticultural oil, you can find it at most garden supply stores.
Not sure if they get good air circulation but spiriea benefit from thinning out old woody branches and rejuvenating pruning to stimulate new growth each year. They can be trimmed back aggressively with no harm. It is also good to keep the winter salt and sand away and not pile too much snow on them in the winter.
I recommend cutting out any branches that look infected and keeping an eye on it. If you see this return in the summer months then it can be treated with horticultural oil, you can find it at most garden supply stores.
Not sure if they get good air circulation but spiriea benefit from thinning out old woody branches and rejuvenating pruning to stimulate new growth each year. They can be trimmed back aggressively with no harm. It is also good to keep the winter salt and sand away and not pile too much snow on them in the winter.
