Now is the time to take action against the crawler stages of magnolia scale, Neolecanium cornuparvum, which are actively moving around before settling down to feed on twigs. The crawlers are usually located on the undersides of 1-to2-year-old twig growth. They eventually produce a powdery, waxy, white covering over their bodies. Magnolia scale overwinters as a first-instar crawler. There is only one generation per year in Illinois.
Magnolia scale females are 1/2-inch long and red-brown in color. They are initially covered with a white, waxy powder. In August and September--depending on the temperature--females produce eggs, which hatch into crawlers that are gray to red in color. The crawler stage is most susceptible to insecticides applied during September. Insecticides recommended for managing magnolia scale include acephate (Orthene), insecticidal soap, and summer oil. It is essential to cover all plant parts thoroughly. Although insecticides are effective in dealing with magnolia scale, the primary way to minimize problems is by promoting plant health through proper irrigation, fertility, mulching, and pruning practices. This may reduce susceptibility or limit injury when plants are infested with low to moderate populations of magnolia scale.
Although there are a number of natural enemies such as ladybird beetles that feed on magnolia scales, they are usually not abundant enough to provide sufficient control.