Noun | 1. | Phytophthora - destructive parasitic fungi causing brown rot in plants fungus genus - includes lichen genera family Pythiaceae, Pythiaceae - fungi having sporangia usually borne successively and singly at the tips of branching sporangiophores Phytophthora citrophthora - causes brown rot gummosis in citrus fruits Phytophthora infestans - fungus causing late blight in solanaceous plants especially tomatoes and potatoes |