Knowledgebase
Magnolia Scale and Red Leaf Maple Spots #875113
Asked June 28, 2024, 1:16 PM EDT
We have a mature Magnolia tree that has Magnolia Scale which appears to be well along since the tree branches are already encrusted with the white sacs. Odd that we would get this in early summer. Any recommendations at this point would be most appreciated . [pictures attached].
Also - just discovered spots on a one yaer old Red Leaf Maple and I don't know if this should be of concern. Can you lease look at the attached pictures and advise. Thanks.
kind Regards,
Craig O'Donnell
Wayne County Michigan
Expert Response
Hello Craig,
The appearance of Magnolia scale or Neolecranium cornouparvum in June, may be due to the warmer temperatures this month.
The scale, excretes a honeydew which is mainly sap that attracts a sooty mold that turns the tops of branches and leaves black. Read more here:
https://www.canr.msu.edu/news/check_magnolias_for_magnolia_scale_now
You will see in that article that controlling the scale depends on the stage of the insect. June to early July is the time to apply systemic insecticide which is absorbed by the roots and will move from the roots into the branches.
The next stage in the insect’s life is the active crawler stage which occurs in Michigan in August through September when you can spray with a contact insecticide. You should not need to use the second application if you do the first.
Always read and follow the instructions on the label for the best result when applying pesticides.
MSU’s Enviro-weather site has a tool which states when the crawlers are active.
http://msue.anr.msu.edu/news/magnolia_scale_is_starting_to_appear_on_magnolias
Finally, if your tree is too large for you to treat, consult a certified arborist. Go to: www.treesaregood.org, the website of the International Society of Arborists to find one in your area.
Although it is difficult to see in the picture, the condition on your Japanese maple could be Phyllosticta leaf spot, a common, but mainly cosmetic disease that affects maples. These spots have tan centers with purple, red or brown margins. Tiny, black, pimple-like reproductive structures often form within the spots. As the spots get older, the centers may fall out leaving circular holes.
It is caused by the fungus Phyllosticta minima which overwinters in leaf litter. In the spring, rain and wind blow the spores onto the developing leaves. These rarely cause significant damage to mature trees. Read more here: https://hort.extension.wisc.edu/articles/purple-bordered-leaf-spot/
MSU Extension’s Plant and Pest Diagnostic Lab can provide a diagnosis of the problem. To learn how to submit a picture/or sample to the lab go to: https://www.canr.msu.edu/pestid/
Thank you for contacting Ask Extension.
