Magnolia Tree concerns

Asked July 24, 2017, 7:48 PM EDT

We just noticed these white larvae type sacks all over the branches of our beloved magnolia tree here in NE Minneapolis. We included pictures of the white sacks as well as some leaves if that is helpful. Our question is what are these things and what can we do to protect/save our tree? (Get rid of these invaders?) Thank you for your help!

Hennepin County Minnesota magnolia magnolia scale

3 Responses

Thank you for the question. Your magnolia tree is suffering from magnolia scale, an insect pest that if left unchecked, can kill the tree because the scale has sucking mouth parts that remove large quantities of sap from branches. According to Michigan State Extension:
" small infestations can be removed any time of year by pruning out infested branches. There are two strategies for treating heavily infested trees. The first option is to use imidacloprid or dinoterfuran as a basal soil drench in August. Check the product label to make sure it has one of those two active ingredients. Homeowners can purchase imidacloprid as “Tree and Shrub Insect Control” or in several other products. Follow the label directions for mixing the product in a bucket of water and pouring it around the base of your tree. It is not known how much risk would be posed to pollinators by a fall soil drench of these products, but it would be less than an application in spring shortly before bloom. The second option, which would pose no real risk to pollinators, is to spray your tree when magnolia scale is in the crawler stage. Watch for the small, reddish crawlers to emerge between the middle of September and early October. As of this writing, August 13, 2015, crawlers have already started to emerge.

Horticultural oils, often called summer oils, applied after the crawlers have emerged in late August can be very effective in reducing the scale population. Be sure to obtain good coverage. Oils can also be applied in fall before freezing weather and again in early spring before the flower buds swell to kill the overwintering nymphs located on the stems. Do not exceed the label rate, which is usually a 2 percent concentration of oil in the spray that is applied. For the professional landscaper or arborist, you can also spray the crawlers with Pyriproxyfen (Distance), an insect growth regulator that is very safe to use. Before using any pesticide, be sure to read, understand and follow the label directions http://msue.anr.msu.edu/news/check_magnolias_for_magnolia_scale_now

The insects may enter the crawling stage sooner in Minnesota. Scout your tree daily.

Thank you for contacting Extension.

Thank you. Do you know of anyone who may be able to come to our home and treat our tree?

As Master Gardeners, we do not refer people to specific businesses. We do recommend that you find a certified arborist to treat your tree if you don't do it yourself. This publication should provide adequate guidance to get you started: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/how-to-hire-a-professional-arborist/