Phyllaphis fagi

The woolly beech leaf aphid is a highly noticeable but typically not a damaging insect pest of European beech (Fagus sylvatica) and its cultivars. This piercing-sucking insect pest will not feed on American beech. It is often referred to as the woolly beech leaf aphid as the undersides of the host plant leaves are where they are most likely to be found. However, they may feed on host plant leaf petioles, fruit, and fruit stems. This species of aphid is gregarious, and often large groups of them are found on host plant leaf undersides along with large numbers of cast skins (shed exoskeletons following the molting of the insect). The woolly beech leaf aphid is "woolly" because of waxy, white filaments that cover the body - giving the aphids or any surface they coat a white appearance. The woolly beech leaf aphid is widely distributed in North America and found throughout the Northeast (essentially wherever European beech and its cultivars are grown.) These insects overwinter in the egg life stage tucked in bark crevices and near buds. Eggs hatch when spring temperatures warm, often near budbreak. Wingless viviparae (parthenogenetic females that give birth to live young) are pale green and covered with white, waxy wool. Wingless individuals are usually 2.0-3.2 mm long. Winged viviparae (parthenogenetic females that give birth to live young) are dark in color and densely coated in white, waxy wool. Multiple generations per year are possible, and in Europe at least 10 generations per year have been reported, with peak activity by mid-June (Iversen & Harding, 2007). As the insects feed on the host plant leaf undersides, they excrete large amounts of a liquid sugary waste product, known as honeydew. Honeydew can be attractive to stinging insects such as ants, bees, and wasps but also a growing place for fungi such as sooty mold. Sooty mold is often black in color and feeds not on the tree itself, but on the honeydew. The woolly beech leaf aphid is native to Europe, and has been introduced to North America, New Zealand, Australia, China, and Korea. Do not confuse this species of aphid with Grylloprociphilus imbricator (the beech blight aphid). The beech blight aphid is only found on the stems of American beech and is sometimes called the "boogie woogie aphid", owing to the fact that when disturbed, G. imbricator will "dance" and wave their rear ends back and forth in a most entertaining unison.