White Fuzzy Balls on Aspen Trunks: Insect or Fungal Canker?

Simple Field Test

Scrape a tiny bit of bark under the cottony mass. Green tissue = insect (woolly aphids or scale). Brown/black dead tissue = fungal canker.

If Insect

• Usually not fatal; tree often looks healthy otherwise.
• Remove a bark section for nursery ID if unsure.

If Fungal

Cankers can girdle and kill branches. Prune out affected limbs, sterilizing tools. No spray cures established cankers.

Since your trees aren’t declining yet, insects are the more likely culprit.