According to statistics and Google Ngram "widely spread" is dying out, and is being used less and less often while "widespread" is becoming popular.
There's also "spreads widely" that is also correct but becoming less popular.
According to statistics and Google Ngram "widely spread" is dying out, and is being used less and less often while "widespread" is becoming popular.
There's also "spreads widely" that is also correct but becoming less popular.