What causes the soapy looking stuff on sycamore trees in the rain

Question

Hi

I was wondering if you could shed any light on this

I was recently in the woods during a sustained rainy day. We noticed what looked like soap suds runing down sycamore trees and wondered what that might or what it might be caused by. Amongst our first thoughts were is there something wrong with the tree this toxic or harmful to plants /animals/ people.

These trees all seemed to have a diameters from 12 -18 inches and appeared to be very tall. Most appeared to have Tar-spot or some thing similar affecting the leaves.

Answer 1

That is nothing to worry about and is just the rain dissolving chemicals from the bark of the tree as it runs down. Air combines to form foam. You see similar foaming where water runs across rocks in a waterfall.