Phytophthora fragariae is a fungus-like (oomycete) plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries and raspberries. Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced flowering, stunting, and bitter fruit. The pathogen is spread via zoospores swimming through water present in the soil, released from sporangia.