Magnolia scale

Asked November 3, 2018, 2:14 PM EDT

It looks like my Magnolia Tree has Magnolia scale. It has scale pods up and down most branches. I noticed it at the end of July when it was swarming with bees, wasps and flies and honeydew showered down from the branches. It is now Nov. 3rd and all the leaves are down and the bark and branches are a dark gray. It looks sick and I would like to know what I can do to help it. Thank

Hennepin County Minnesota

2 Responses

You have probably read about magnolia scale but following is a detailed account of this insect's life cycle and ways to deal with it. The scales aren't easily controlled and can not be killed with insecticides during much of the year.

This excerpt from a University of Wisconsin publication lists insecticides that can be effective if they are applied at the appropriate time:

"Control of magnolia scale can be challenging. Only young, mobile crawlers are easily controlled. If you decide to use spray treatments for control, select a product that contains bifenthrin, carbaryl, cyflulthrin, horticultural oil, insecticidal soap, malathion, or permethrin. Proper timing of the application of these products is critical. Apply spray treatments in late August or early September and follow with a second treatment 10 to 14 days later. Systemic insecticides, such as those containing imidacloprid, have also been effective in magnolia scale control, but such products must be drenched into the root zone in early May. Finally, dormant oils can be used for control, but must be applied in March, before buds open. Be sure to read and follow all label instructions of the insecticide that you select to ensure that you use the insecticide in the safest and most effective manner possible."

The dark gray color of the branches is probably the result of a fungus called sooty mold that grows on the honeydew deposited by the scales.