In much of Illinois, it is time to treat for the second generation of the infamous pine needle scale, Chionaspis pinifoliae. In general, egg hatch occurs when Vanhoutte spirea is in bloom but may be later, depending on environmental conditions. The young crawlers, which move around on the plant, are much more susceptible to pest-control materials than are the mature adults. Pine needle scale attacks mugo, Scotch, Austrian, and red pines.
Mature pine needle scales are small (less than 1/8-inch long), elongated, white scales located on pine needles. Eggs overwinter underneath the scale cover of the mated adult female. From late May through June, eggs hatch into crawlers that move around on the foliage before finding a place to settle and feed. They remove fluids from the mesophyll layers of needles with their piercing--sucking mouthparts, causing the needles to turn yellow, then brown. Pine needle scale is a hard scale, so no honeydew is produced during feeding. Whole branches and even entire trees may be killed under heavy infestations. Crawlers may be blown onto other plants by wind. There are two generations per year in Illinois.
Managing pine needle scale involves maintaining plant health and using pest-control materials. Proper cultural practices, such as watering, fertility, and mulching, go a long way to minimize stress and allow plants to tolerate low to moderate populations without injury. Pest-control materials recommended include acephate (Orthene), insecticidal soap, and summer oil. The second-generation crawlers may be treated when Hills-of-Snow hydrangea blooms turn from white to green. Repeat spray applications 7 to 10 days later because the second-generation eggs hatch over a longer period. Be careful when using summer oil, as it may discolor plant foliage.