heeeeelp! Lightmapping Artifacts

hello guys,
I’m doing lightmaps with unity,
This is the result
Imgur
how can I fix these errors?
thanks

One solution, I open lightmap file in photoshop and eliminate errors, but when I save the map in unity, I see no changes!!?

open texture (lightmap) in photoshop,
I correct problems (dirt) and export
the result but 'is blue!
here is picture
Imgur