South Perth Summary Describes symptoms, identifying characteristics and control measures for carrot leaf blight and carrot leaf spotting. Carrot leaf blight is a disease commonly found in carrot crops in Western Australia. Carrot leaf blight is usually caused by the fungus Alternaria dauci and occasionally by A. radicina . Another fungus, Cercospora carotae , causes a leaf spotting of carrots. Both Alternaria and Cercospora can weaken leaves and in severe cases can defoliate crops.
Mechanical harvesting is difficult when leaves are weakened by blight.
Alternaria dauci is more common in autumn and winter and Cercospora carotae is more common in summer. It is possible for both types of fungi to be present at the same time in a crop. Symptoms Alternaria dauci appears on leaves as small variously-sized dark brown to black lesions. The lesions often appear on the edges or margins of the carrot leaf. In severe cases, the lesions expand, causing the leaflets to turn brown, shrivel and die.