[john70t]

Preconditioning is essential.
Wet down everything before getting to it.
(I'll post another thread on power washing and staining.)

We've had rather mild winters with more outside mildew recently in Michigan.
Never seen it before.
Everything around here gets "dirty" too quickly.
Use "Wet n forget" on everything inorganic using a container sprayer and dilution directions 1:5.
It seems to be a decent product for prevention.
It needs a week of dry heat followup afterward to work best.
It is mild for most plantings.