Phoma stem canker (blackleg) caused by Leptosphaeria maculans attacks many brassica crops (especially rape) and can spread rapidly within a field. Plants can become infected at the seedling stage or at any stage in the field. Symptoms of the blackleg start as slight lesions on stems at cotyledon scars which elongate, turn brown with a black to purplish border, and become sunken. The lesion extends up and down the stem, and the stem becomes girdled and blackened, with many fruiting bodies (pycnidia) embedded in the tissue. Lesions may extend below the soil and attack roots. Diseased plants often wilt, lodge, and die. On root crops, symptoms occur in the form of cankers on the fleshy roots and a dry rot may appear in storage.