Posted on August 27, 2015
Magnolia scale is becoming a common problem on magnolia trees in Wisconsin. Star magnolia (Magnolia stellata) and saucer magnolia (Magnolia x soulangiana) are very susceptible to this insect.
Magnolia scale is a soft insect. It sucks plant sap, and excretes large amounts of drippy, sticky honeydew. This honeydew provides an excellent growth medium for sooty mold fungi giving leaves and branches a black, sooty appearance. This honeydew and sooty mold can stain lawn furniture and other items in the vicinity of an infested tree. Sugars in the honeydew can attract wasps and ants. In addition, trees that are heavily infested can have substantial weakening of branches and branch dieback which can lead to eventual tree death
Magnolia scale has one generation per year and overwinters as nymphs on one and two year old branches. Nymphs mature in early June, when adult females begin to lay eggs that hatch in late August. Control of magnolia scale can be challenging. Treatment is usually recommended in late August or early September. For treatment recommendations and more information, see http://hort.uwex.edu/articles/magnolia-scale/
Photo by UW Insect Diagnostic Lab, UW-Extension
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