Beech blight aphids (Grylloprociphilus imbricator). American beech trees usually survive their infestation.
Photographer: Ery Largay, courtesy of NatureServeIn autumn, you may see long, stringy, white woolly masses on American beech twigs—colonies of hundreds of little aphids that do an entertaining dance-like sway when agitated. This is the beech blight aphid (Grylloprociphilus imbricator), a native insect that relies on American beech trees for habitat. Though the sooty mold that can collect on their sugary excretions may be aesthetically displeasing, the beech blight aphid is generally not considered a problem in its native range in the U.S. Though some years it is more populous, natural parasites or predators such as carnivorous Harvester butterfly caterpillars feed on it and bring its numbers back under control.1  2

• 1. University-of-Massachusetts-Extension.  2002.  The Beech Blight Aphid.
• 2. Cook CW.  2008.  American beech (Fagus grandifolia) .