A lesson on pine bark adelgid

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.   

Pineus strobi (Homoptera: Adelgidae) is found throughout the United States wherever white pines grow. This insect is quite small, dark and covered with white, waxy strands. Infested trees can be recognized by the presence of patches of this white, cottony material on the smooth bark of the trunks and limbs and at the bases of needles. Heavily infested trees may appear whitewashed. The insect uses its long, needle-like mouthparts to pierce the tree bark and feed on the sap.

According to Howard Russell, MSU Diagnostic Services, “The adelgid overwinters as nearly mature female nymphs that begin feeding during the first warm days of spring. When mature, the females begin to lay eggs that begin to hatch in late April in Michigan. These eggs produce both wingless and winged forms. The wingless forms fly off to nearby spruce trees to lay eggs but the offspring from these eggs eventually die. The wingless forms that remain on the white pine produce as many as four more generations during the growing season. Healthy trees do not appear to suffer any permanent damage from pine bark adelgids, however, the cottony patches may affect the overall appearance of the tree.”

Pine bark adelgids seldom require chemical control measures to protect the health of the tree. If large numbers persist and the tree becomes unsightly, then dormant oils, superior (summer) oils, and insecticidal soap will reduce aphid numbers without harming beneficial insects. A more aggressive control strategy is to spray the trees in late spring or early summer with a broad-spectrum insecticide. These sprays will destroy the natural enemies of the many potential pest species that feed on pines so they should be used only after attempts have failed to control the aphids. Be sure to read and follow all the instructions and safety precautions found on the pesticide label before using any pesticide.

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