Hello Carman,

Based on your image, this appears to be Phyllaphis fagi, commonly known as woolly beech aphids. These little fluffballs are known for their white, waxy coating and tendency to gather in large colonies on the undersides of beech leaves. More information at these links:

Managing Pests in Gardens: Trees and Shrubs: Invertebrates: Woolly Aphids—UC IPM

Woolly Aphids on Trees | University of Maryland Extension

Are They Harmful?

To the tree: Woolly beech aphids feed by sucking sap from leaves, which can cause leaf curling, yellowing, and premature drop. However, healthy mature beech trees typically tolerate infestations without severe long-term damage. More information at this link:

Aphids - Integrated Pest Management

To humans or pets: They’re not harmful to people or animals, though their sticky honeydew can attract sooty mold and make surfaces beneath the tree messy. More information at this link:

Aphids - Integrated Pest Management

Best Treatment Options

If the infestation is heavy or the tree is young and stressed, here are some management strategies:

Natural predators: Lady beetles, lacewings, and parasitic wasps often keep aphid populations in check.

Horticultural oil or insecticidal soap: These are effective and environmentally friendly options. Spray directly on the aphids, especially on leaf undersides.

Water blast: A strong stream of water can dislodge aphids and reduce their numbers.

Avoid harsh chemicals: Broad-spectrum insecticides can harm beneficial insects and disrupt the natural balance.

For more detailed guidance, you can check out Michigan State University’s IPM resource or the University of Maryland Extension’s page on woolly aphids. More information at these links:

Aphids - Integrated Pest Management

Woolly Aphids on Trees | University of Maryland Extension

I highly recommend sending your image by email to the MSU Plant & Pest Diagnostics Lab to receive a confirmed and precise diagnosis and identification.

Their email is <personal data hidden> - Please include your first and last name.

The experts there can also provide you with the best treatment options.

The lab will let you know if they need a sample sent.

The lab may also ask for additional images. So be prepared.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details on submitting a sample to the MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu)

I hope this helps!