Emerald ash borer and Asian longhorned beetle are notorious in the forest pest world, but there are other species to know, too. A recent training on invasive forest insects called attention to balsam woolly adelgid. BWA wasn't the star of the show; in fact, it wasn't even on the program; but its damage to balsam was evident in Indian Lake, where the training was held, and prompted discussion.
In the days following the training, I received two other inquiries about the cause of visible damage on balsam trees. One described dead and dying balsam near Lake Abanake, also in the Indian Lake area. Another described round exit holes and munching sounds coming from balsam in the High Peaks region. It was time for some forest pest sleuthing.
Luckily, invasive species specialists in the Adirondacks and New York are well connected. I reached out to contacts at the state Department of Environmental Conservation, United State Department of Agriculture and Cornell. Fortunately, the munching and exit holes were not a concern. The culprit was probably the white spotted pine sawyer, a common native insect that feeds on dead and dying conifers, including balsam. Experts did confirm, however, that there are localized BWA infestations in the Adirondacks, which may have been the cause of mortality near Lake Abanake.
Symptoms of a balsam woolly adelgid infestation include dead or dying trees with swollen, deformed branches or foliage that turns yellow then deep red or brown.
(Photo courtesy Dawn Dailey O'Brien, Cornell University)
Balsam woolly adelgid is an aphid-like insect that produces a waxy wool-like material to cover itself and protect its eggs.
(Photo courtesy Robert L. Anderson, USDA Forest Service, Bugwood.org)
Balsam woolly adelgid (Adelges piceae) is a European species introduced to the U.S. in the early 1900s, likely from infested nursery stock. It is a wingless, aphid-like insect that causes extensive mortality in true fir (Abies). Adults are tiny (about 1mm long), dark purple to black and nearly spherical. They produce a thick mass of a waxy, wool-like material that covers the body and protects the adult and eggs. Eggs hatch into amber colored "crawlers," which is their only mobile stage. Spread appears to be by wind or transport on birds and other animals.
Adelgids feed on branches and twigs, which causes severe gouting, or swelling, around the buds and branch nodes and slows the growth of buds and needles. Tree crowns can appear deformed, looking "fiddle-shaped" or "top curled." Tree decline may occur over a decade or more. Heavy infestations on the bark of the trunk cause abnormal growth of the vascular tissue, which is the tree's lifeline for nutrients and water. Foliage in a dying tree turns yellow then deep red or brown, and death can occur in two to three years. The adelgid also increases the risk of mortality in times of drought, since high elevation species such as balsam are particularly vulnerable during these events.
Severe infestations are noted in southeastern forests, such as in the Great Smokey Mountains National Park, and in forests of the Pacific Northwest. Not much is known about its distribution or impacts in the Adirondacks, though DEC's forest health team has started tracking BWA in recent years.
Biological controls have not been successful in limiting BWA, and chemical controls are ineffective when treating infestations over large areas, but weather may be on our side. Extended months of cold winter temperatures and a shortened summer season can result in less reproduction or possibly limit the distribution. So for now, cold winters may be helping to keep BWA at bay.
Balsam is an important tree in our region. It is a major food of moose during the winter and provides valuable wildlife habitat for small mammals and birds. The balsam tree canopy along streams can protect water quality and fish populations downstream. It is also a popular tree used during the holidays for decorating, making wreaths and using its fragrant needles as stuffing in pillows.
Be on the lookout for balsam woolly adelgid. Report sightings or email photographs of signs and symptoms to the Adirondack Park Invasive Plant Program at 518-576-2082 or email@example.com. Additional information can be found at www.na.fs.fed.us/pubs/fidls/bwa.pdf.
Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at www.adkinvasives.com.