Powdery mildew
Powdery mildew is one of the more recent diseases of carrots. It was first discovered in 1975 in the United States in the warmer climates of California and Texas. Powdery mildew will cover the carrot with a film of white fungal growth which does not kill the plant, but stunts the growth of the carrot. These weaker plants are nearly impossible to harvest mechanically.