Pythium sulcatum causes diseases predominately on members of the apiaceous family, the most common being the carrot.

[2] P. sulcatum is also seen to cause damping off, taproot dieback, root rotting, stunting, and forking of carrots, with cavity spots being the most common of these diseases.

[3] The pathogen overwinters in the form of an oospore, which can survive several years in the soil and inoculates the host when temperatures become optimal.

[2][5] Pathogenesis begins with the germination of resting spores (oogonia and hyphal swellings), that occurs quickly in response to root exudates.

[5] P. sulcatum is associated with its ability to produce a wide array of cell wall degrading enzymes with significantly high enzymatic activity.

It is postulated that the sequence of enzymic production, in association with a slow growth rate, affects the plant infection response which causes the types of symptoms characteristic of this Pythium species.