Figure 10 Pythium root dieback symptoms on carrots. Figure 11 Pythium root dieback symptoms on carrots. It is a post-harvest disease associated with carrots stored at high temperatures and humidity. The symptoms typically develop after the carrots have been washed and packaged in plastic and not stored at proper temperatures. Field symptoms are not seen.
Carrots damaged during packaging are more likely to become infected.
Careful harvest handling and storage at proper temperatures from harvest to sale are the key management suggestions. Figure 13 Black root rot. Be sure to purchase clean and treated seed and follow the management guidelines recommended for Pythium diseases. In addition, an eight year rotation away from carrots, parsnips, parsley and celery and deep plowing of crop residues are recommended in infested fields. Both raised and sunken, dry, corky lesions may form on the carrot root, however, symptoms are rarely severe enough to cause major yield losses.