Despite the cool weather we have experienced recently, in most portions of Illinois it is time to treat for pine needle scale, Chionaspis pinifoliae while Vanhoutte spirea, Spiraea x vanhouttei, is blooming. During this time, eggs that have hatched into young crawlers are moving around on plants, looking for a place to insert their mouthparts and begin the process of feeding. The crawler stage is the most susceptible to insecticide applications and sprays of a hard stream of water (Remember, water is not a registered pesticide. . . yet!!!). Mugo, Austrian, Scotch, and red pines are the most susceptible to attack from pine needle scale.
Mature pine needle scales are elongated white scales 2 to 3 mm in length on the needles of evergreens. Pine needle scale overwinters as eggs underneath the mated female scale cover. A females can lay up to 100 eggs during her lifespan. The eggs hatch into small crawlers from about late April through June, depending on the environmental conditions—particularly temperature. Crawlers move around on the needles before finding a place to settle and feed. The crawlers withdraw plant fluids from the mesophyll layer of the needles, causing the needles to turn yellow, then brown. Under heavy populations, entire branches may be killed. In fact, entire trees may be killed, particularly pine trees that are stressed. Young crawlers may be blown onto other plants by wind—starting a new infestation. In general, there are two generations per year in Illinois.
Management of pine needle scale involves sustaining plant health and using insecticides accordingly. Properly implementing cultural practices—including irrigation, fertility, mulching, and pruning. Minimize stress and allow plants to tolerate “low” to “moderate” populations of pine needle scale without experiencing injury. Insecticides recommended for controlling pine needle scale include acephate (Orthene), bifenthrin (Talstar), cyfluthrin (Tempo), insecticidal soap, and summer (= horticultural) oil. These insecticides should be applied when Vanhoutte spirea is blooming. Second-generation crawlers may be treated when Queen Anne’s lace is in bloom. Repeat spray applications 7 to 10 days later may be needed because second-generation pine needle scale eggs hatch over an extended period