The Collaborative International Dictionary of English v.0.48:

Putresce \Pu*tresce"\, v. i. [See Putrescent.]
   To become putrescent or putrid; to putrefy.

         Ordinarily sewage does not putresce until from
         twenty-four to sixty hours after its discharge.
                                                  --Nature.
   [Webster 1913 Suppl.]