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Treating Magnolia Tree Disease #872923

Asked June 13, 2024, 11:05 AM EDT

My magnolia trees have a disease again - white rounded spots, sweet dark sap dripping. I used to ask our Farm Bureau people what to use (it was a concentrate diluted with water and poured around the base of the tree), but they have closed and I don't remember the name of the product. I'd appreciate advice on what to use to treat this'

Barry County Michigan

Expert Response



Hello,
Yes, I agree that you have magnolia scale on this tree. Treating scale effectively relies on proper timing of the product that you use. Your best option at this point is to wait until sometime in August to spray with a product that contains bifenthrin, carbaryl, cyflulthrin, horticultural oil, insecticidal soap, malathion, or permethrin. You will begin to see the immature insects begin to emerge from under the armor you see now. Initially, they cover themselves with a white waxy protective coating, but later in August (it may be a little earlier this year), this coating begins to break down and the insects are more vulnerable to the spray. You will need to spray again a few weeks later. If it is a very heavy infestation, and you are doubtful you eradicated the scale, you may also want to do some dormant oil early next spring before the buds open or wait until May and use a root drench product containing imidacloprid. Here is a good article that explains it very well. Always read the label to find a product that is appropriate for magnolia scale and follow the directions.
https://hort.extension.wisc.edu/articles/magnolia-scale/
I hope this is helpful.
Thank you for contacting Ask Extension.
Ruth

An Ask Extension Expert Replied June 14, 2024, 4:40 PM EDT
Great information.  Thank you very much!


On Fri, Jun 14, 2024 at 4:40 PM, Ask Extension
The Question Asker Replied June 14, 2024, 11:31 PM EDT

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