Magnolia Scale

Asked June 29, 2016, 3:50 PM EDT

Both my Star and Merril Magnolias have become infected with Magnolia scale. It probably appeared two years ago, but I didn't pay attention to it. By last year, I lost two large branches on my 40 year-old Star Magnolia and now my 25 year-old Merril is getting badly infected. Where does the scale bug come from? Is it a blight spreading across the US? How does the MN Landscape Arboretum treat the disease? Is Horticultural oil sprayed in August the best treatment -- when in August? Can my beautiful trees be saved? Please help!

Anoka County Minnesota

3 Responses


Here is some good information from a couple of sources. Please note, however, that these articles were written before the tragic effects of imidacloprid on pollinators were known. The articles are provided for the other information they contain, Dormant oil sprays can be done by homeowners and if the timing is right are effective. It does take vigilance and persistence.


The first link you included is no longer available. The second link you included I previously read and question since it states that the recommended treatments are only valid in Kentucky. I need some real help here before my trees die. I hope the staff at the MN Landscape Arboretum will have more facts, advice and treatments I can use to solve this serious problem.