Is dieresis dieretic?

The correct spelling of the word should be diaeresis

There is some confusion here about which what word you're querying. I could find no such word as dieretic.

Are you perhaps referring to a diacritic mark?

OTOH, Diuretic is a word but this word has no connection to language or phonetics. Diuretic is a substance/pharma product that aids in producing urine.
http://en.wikipedia.org/wiki/Diuretic

Dale is playing with words but he is not being caustic enough..

Not everybody can be diaeretic.

My Webster allows either way

Me nuther, Rag. I was being funny (I thought)

oh ok. sometimes I'm slow on the uptake.

Rag you're forgiven by incredibly slow oldster