Woolly beech aphid

The woolly beech aphid, Phyllaphis fagi, is an introduced aphid which can be found on Fagus sylvatica. Growers report seeing them on several cultivated varieties including Fagus sylvatica'Asplenifolia', 'Fastigiata', 'Roseo-Marginata' and 'Purpurea

Young aphid nymphs have been found to hatch (eclose) from overwintering eggs before bud break (Iverson and Harding, 2007). In Oregon we have had reports as early as mid-April but they become more noticeable in May. These aphids will feed and soon reach adult stages. They reproduce without mating (parthenogenesis) so populations of aphids on the spring growth can enlarge rapidly. As many as 10 generations were documented in nursery production (Iverson and Harding, 2007). Winged (alates) aphids are produced for months and winged populations peak in mid-June. No significant difference in reproductive fecundity was seen between winged and wingless females (Iverson and Harding, 2007). Winged males mate with wingless females in the fall. Those females lay eggs on stems which overwinter.

Monitor for the eggs near buds and the aphids on new growth and leaf undersides.

For information on management of aphids, check the PNW Insect Management Handbook.


Nice images can be found at Invasives.org: Woolly beech aphid

There is a discussion of woolly beach aphid at the plante doktor website.

Iversen, T. and Harding, S. (2007), Life table parameters affecting the population development of the woolly beech aphid, Phyllaphis fagi. Entomologia Experimentalis et Applicata, 123: 109–117. doi:10.1111/j.1570-7458.2007.00524.x <24 Mar 2016>


Fan-dancing woolly beech aphids - video


Orginal publication 4/20/06
Lastest revision <8 May 2017>

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University/NWREC.

Woolly beech aphid eggs on stem

Photo: Rosetta

A microscopic shot of an aphid on the leaf underside. The "wool" has been knocked off of the aphid in transport.

Photo: Rosetta

A white tuft near the yellow arrow shows the small size of the aphid.

Photo: Rosetta

A colony of woolly beech aphid. Note honeydew near aphid.

Photo: Invasives.org

Woolly beech aphid colony in late June

Woolly beech aphid colony in mid-May

Photo: Rosetta, Oregon State University