magnolia with lots of flys, bees, ants and powdery mildew on branches - Ask Extension
I have a magnolia tree that has white growths on the branches that look like powdery mildew. The white areas shed a light powdery dust when rubbed. ...
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magnolia with lots of flys, bees, ants and powdery mildew on branches #661359
Asked July 08, 2020, 10:15 AM EDT
I have a magnolia tree that has white growths on the branches that look like powdery mildew. The white areas shed a light powdery dust when rubbed. The hostas below the magnolia have a black film that comes off if rubbed hard. It looks like dirt that has accumulated on the hosta leaves, but it adheres more tightly than dirt would, i.e. it does not wash off easily with a water hose.
I also noticed a very large number of flies, bees, wasps, and ants on the magnolia. They appear to be sucking something off of the leaves, but I can not see any aphids or "honeydew" secretion. Please see pictures below.
I was planning on spraying with a fungicide, but now I wonder if I should first spray with an insecticide before using the fungicide. Any ideas on how to proceed?
I greatly appreciate your advice!
Thanks,
Steve Bishop<personal data hidden>
Ramsey County Minnesota
Expert Response
Thank you for writing.
The pictures of the leaves and branches and stems are not close enough.
There are several possibilities.
Aphids with honeydew. https://extension.umn.edu/yard-and-garden-insects/scale-insects
Fungus
Please send me additional photos of the leaves and of the stems and of the hosta below.
The pictures of the leaves and branches and stems are not close enough.
There are several possibilities.
Aphids with honeydew. https://extension.umn.edu/yard-and-garden-insects/scale-insects
Fungus
Please send me additional photos of the leaves and of the stems and of the hosta below.
Here are some additional close-up pictures. This looks a lot like Magnolia scales per the article that you referenced above. https://extension.umn.edu/yard-and-garden-insects/scale-insects#soft-scales-on-deciduous-trees-860011 Some of the larger nodules had a 1/4 inch brownish red thing (insect, I think) that released a pink sticky liquid when squeezed.
Do you have a recommendation for a pesticide from the list in the article? I have permethrin available - would that work?
A few of the Magnolia leaves have the dark coloring as shown in the Hosta pictures, but most of the Magnolia leaves are green. I do not see any signs of aphids or honeydew, but maybe they are so small that I can not see them.
There is a room air conditioner in the window next to the Magnolia that blows hot air towards the tree, could this be part of the problem?
Thanks for your help with this problem!
Do you have a recommendation for a pesticide from the list in the article? I have permethrin available - would that work?
A few of the Magnolia leaves have the dark coloring as shown in the Hosta pictures, but most of the Magnolia leaves are green. I do not see any signs of aphids or honeydew, but maybe they are so small that I can not see them.
There is a room air conditioner in the window next to the Magnolia that blows hot air towards the tree, could this be part of the problem?
Thanks for your help with this problem!
More pictures of Magnolia scale
Thank you for writing back. I would try non-pesticides first. Any pesticide against aphids will be hard on pollinators. You live in ramsey county. The large garden centers will sell fresh ladybugs in bags from a refrigerator. One bag will be enough. Towards dusk mist the plant with water and gently open the bag of lady bugs and shake it around the plant. By eating the aphids, they will stop the scale. The ladybugs will disappear in two or three days. Drop me a note on how it works.
https://blog.bugsforgrowers.com/natural-predators/ladybugs-can-control-of-aphids-mealybugs-mites-scales-and-thrips/#:~:text=Both%20larvae%20and%20adults%20of,bugs%2C%20mites%20and%20scale%20insects.&text=For%20example%2C%20once%20ladybugs%20are,start%20feeding%20on%20their%20prey.
https://blog.bugsforgrowers.com/natural-predators/ladybugs-can-control-of-aphids-mealybugs-mites-scales-and-thrips/#:~:text=Both%20larvae%20and%20adults%20of,bugs%2C%20mites%20and%20scale%20insects.&text=For%20example%2C%20once%20ladybugs%20are,start%20feeding%20on%20their%20prey.
