Atticus repeatedly characterizes people of certain qualities as trash. These people are exemplified only by members of his own race, but Atticus' descriptions of "trash" would seem to include people of any race or color. 

The Ewells are the prime example of Atticus' definition of trash, but he specifically defines them as trash because of what they do (and what they believe).

Mr. Raymond Dolphus, while of reputable old southern family, is shunned by the others whites of Maycomb because he has a black family.  The Cunninghams have little and are shunned by the townspeople.

Lula scorns Calpurnia's attempt to bring Jem and Scout to the First Purchase Church. The Ewells are looked down upon, even by Atticus. The country folks of Old Sarum are held in low regard by many people. Miss Caroline is questioned because she is from Northern Alabama. The Misses Tutti & Frutti are considered eccentrics because they are deaf and Republican.

I guess the major example in the white community would be people's attitudes towards the "poor white trash" like the Ewells.  They are looked down upon by other whites.  As for Lula, I don't think that fits because that's not within her own race.