Black scale on trees

[sehitchman]

This is a church I cut, I do not have an applicators license. They asked me if I knew how to treat it so thought I'd ask the LawnSite Knowledge base.
The trees are stressed in the summer due to no irrigation, planted next to a huge asphalt lot and the top of a ridge in rocky soil, so the ground does not retain much moisture. The East side of both trees is the blackest, they look like they were burnt. Thanks for looking.

[Cadzilla]

It may be Lichen. Hard to tell from the pics. Natural. Causes no real damage.

[sehitchman]

it is more like a powder