ˌpithēəˈsistə̇s noun
Usage: capitalized
Etymology: New Latin, from pythia- (from Pythium ) + -cystis
in former classifications : a genus of fungi (family Pythiaceae) comprising a single species ( P. citrophthora ) that causes brown rot of citrus fruits and gummosis of citrus and other fruits and is now usually included in Phytophthora