In many parts of Illinois, it is time to treat for pine needle scale, Chionaspis pinifoliae. In general, egg hatch occurs when Vanhoutte spirea is in bloom. The young crawlers, which move around on the plant, are much more susceptible to insecticide applications. Mugo, Scots, Austrian, and red pines are susceptible to attack by pine needle scale.
Mature pine needle scales are small (2 to 3 millimeters long), elongated white scales that are located on the needles of evergreens. Eggs overwinter underneath the mated adult female scale cover. Females can lay up to 100 eggs. The eggs hatch into crawlers from May through June. The crawlers move about on the plant foliage before finding a place to settle and feed. They suck juices from the mesophyll layer of needles, which causes the needles to turn yellow, then brown. Whole branches may be killed. Heavy scale infestations can kill trees. The young crawlers may be blown onto other plants by wind. There are two generations per year.
Management of pine needle scale involves maintaining plant health and using insecticides. Proper implementation of cultural practices, such as irrigation, fertility, and mulching, will minimize stress and allow plants to tolerate low to moderate populations of pine needle scale without suffering injury. The insecticides that can be used to manage pine needle scale include acephate (Orthene), chlorpyrifos (Durs-ban), diazinon, insecticidal soap, and summer oil. These materials are applied in late May or when Vanhoutte spirea is in bloom. Second generation crawlers can be treated as hills-of snow hydrangea blooms turn from white to green. Repeat spray applications 7 to 10 days later, as the second-generation eggs hatch over a longer period of time. Be careful when using summer oil as it may discolor foliage.