I couldn't tell you if it was caused by bugs, a virus, or aliens, but I do remember it caused people to dry up; basically their insides became dust/powder. I want to say this came out in the late 80's or early nineties, and if my memory serves me correctly, the movie has a yellowish tint to it, like it was filmed around the mojave desert/california region.

Possibly Where Have All the People Gone (1974) (TV) (http://www.imdb.com/title/tt0072400/)
YouTube - Where Have All the People Gone - Part 1 (http://www.youtube.com/watch?v=2VaZN3caUsc)

Another possibility is The Andromeda Strain (http://www.imdb.com/title/tt0066769/).

Could maybe be this one I saw a while back?
Set in the LA valley, with a red sky due to the comet.

Night of the Comet (1984) - Plot summary (http://www.imdb.com/title/tt0087799/plotsummary)

The plot summary refers to "a guy who looks like Erik Estrada", who is in fact a young Robert "Chakotay" Beltran.

How can 2 different answers both be correct? I'm feeling a little left out here... Ha

How can 2 different answers both be correct? I'm feeling a little left out here... Ha

I haven't checked out Night of the Comet yet... so that may have the desert scene I'm thinking of, therefore your answer still has a chance. The other answers ARE indeed movies where people turn to dust (and quite enjoyable), but they don't "ring my bell," which has caused me to recheck my sanity on this one. I'll get back to you when I see Night of the Comet.