Pine bark adelgids covered in white, waxy fluff on a white pine tree. / Photo Credit: Wisconsin DNR

Michael Hillstrom, DNR Forest Health Specialist, Fitchburg
Michael.Hillstrom@wisconsin.gov

Pine bark adelgids are tiny, aphid-like insects that suck the sap of white pines. The bugs protect themselves from predators with a fluffy, white wax covering. Pine bark adelgids generate concern when thousands of them gather on white pines to feed, making the pine bark appear covered with sap.

Pine bark adelgids have a variety of predators and generally cause minimal damage to healthy, established white pines. No tree impacts have been noted, even with the drought in 2023. The adelgids can have greater impacts on young white pines, causing needle stunting, discoloration and stress that could lead to mortality in severe infestations.

Chemical control is rarely warranted, except on young trees. Consider using a high-pressure jet of water, insecticidal soaps or horticultural oils on the adelgids; these approaches will protect natural enemy populations. Use traditional insecticide sprays only as a last resort.

White pine trees infested with pine bark adelgids appear sap-covered from a distance. / Photo Credit: Wisconsin DNR