Magnolia Bug/Disease Concern

Asked June 6, 2016, 3:35 PM EDT

Hello - We had a magnolia for several years and it had a hard-shelled bug on it and eventually killed our magnolia tree. Three years ago we purchased another magnolia and this weekend we noticed the following. Attached are 3 photos to indicate the problem. Bachman’s told us they are insects with a hard outer shell (like a turtle). They appeared mostly on the north side of the tree away from the sun; there is some on the top around the newest shoots growing. The bug/shell emits a sticky coating on the leaves that eventually turns the leaves black. Bachman’s said t spray the plant with “Neem Oil” in the spring after the thaw and before leaves out to kill the insect larvae. Unfortunately, our new magnolia (this is going to be its third summer) has started to get the little bugs as you view on the attached pictures. Thank you for any help / suggestions you may have to save our Magnolia. We love our magnolia and want to save it. Thank you. Gloria Goldberg 612-310-7445

Ramsey County Minnesota trees and shrubs insect issues plant disease insect damage magnolia

5 Responses

Your magnolia has oystershell scale. That is an insect that hides under the shell-like cover. Magnolias seem to be quite attractive to scale. I have known people who actually have scraped as many as possible off their tree in combination with the
insecticides. Here is information on this scale:
http://www.extension.umn.edu/garden/insects/find/scales/armored-scales-deciduous/
The insects on the leaves look like aphids. They suck the juice out of a leaf. A strong spray of water will dislodge them. Make sure to get the underside of the leaves. You can do that several times and also can use an insecticide if necessary.

Reference: Question: 329378 Thank you for your information in your email of last June. Is there anything we can spray on the plant in the spring to treat for this insect; kill the eggs/larvae? I manually removed a large number of them last summer and our magnolia is growing like crazy. In a few years I would need a ladder to scrape off the bugs. Thank you in advance for your prompt reply to our second question.....Regards, Gloria & Daniel

It is time right now to apply horticultural oil. You can find it at garden centers. Here is the link again to scale on your tree: http://www.extension.umn.edu/garden/insects/find/scales/soft-scales-deciduous/

Hello - Well, unfortunately, we had an arborist out to also look at the Magnolia and he said do not bother with the oil because our magnolia is dying; and it is now officially dead. This is our second magnolia that has not made it. We would like to move on to another flowering bush (similar to the magnolia) and we are wondering if you could make some suggestions; we are not interested in wegelia or hydrangeas. We would like the plant to get to 4-5 feet tall and the location gets Eastern sun and some of the Southern sun. Thank you for any suggestion you may have.

If you want a shrub that blooms and gets up to 4-5 feet tall, I am going to suggest you look at hydrangeas even though you say you aren't interested. There are many, many varieties with beautiful flowers and right in the size range. I don't know what experience you have had with hydrangeas in the past but the selection now gets better and better each year. I would discourage you from selecting Endless Summer or similar large leafed hydrangeas and instead look at Vanilla Strawberry, Pink Diamond, Little Lime, etc. You will find them grouped together on the lot of a full service garden center.