P. brassicae may refer to:
Phyllosticta brassicae, a fungal pathogen Phytometra brassicae, a moth that is very destructive to plants Phytophthora brassicae, a water mould Pieris brassicae, a pest butterfly Plasmodiophora brassicae, a plant pathogen Pyrenopeziza brassicae, a plant pathogen