My magnolia is infested with magnolia scale. What are my control options?
Magnolia scale is the largest scale insect in Iowa. Sap feeding by the scales causes stress to heavily infested plants and can result in stunted growth, yellowish foliage, branch dieback, or death of the plant. Magnolia scales produce large quantities of honeydew (sugary excretion) that accumulate on the tree’s leaves and twigs. Sooty mold, a black fungus that grows on honeydew, turns the honeydew-covered leaves and twigs black.
To control magnolia scale, remove and destroy heavily-infested branches. Treat with a contact insecticide (horticultural oil, insecticidal soap, other synthetic insecticide) or a systemic insecticide (imidacloprid) in late August or early September. Dormant horticultural oil can also be used in late fall or early spring.