Bacterial blight of carrot

Symptoms
Initially appear as small yellow angular spots that expand to irregular dark brown water-soaked lesions on leaves, stems and petioles, blight of partial or entire umbels, often surrounded by a yellow halo. Lesions are common at the "V" shaped junction of the leaflet lobes. On flower stalks a gummy bacterial exudate may develop.

Treatment
Appropriate action by growers should be ploughing in of infected foliage debris after harvest and to use a suitable 2-3 year rotation.

Prevention
Since the bacterium is a common contaminant of carrot seed, the use of pathogen-free seed or hot water-treated seed is necessary. Copper-based bactericides can slow development of leaf blight in the field.