White foam (fungus) on treated wood

Q: We recently saw a strange white foam substance on our landscape wall. Any help would be appreciated.

A: It is the fruiting body of a fungus that is inside the wood, decomposing it.

See Fungus on Treated wood

Look for the plastic tag on the end of your timbers. It will say who manufactured them and give you contact information and notes on their guarantee.

I think the timbers will need to be replaced.