First and foremost, adhering to Best-Practices for Carrot Culture is the ounce of prevention that puts you ahead of disease pressure. Second, because inadvertent damage to roots, whether incurred mechanically or by pests, can often lead to secondary infections, it's wise to scout frequently, so you can apply the pound of cure before it spreads.
Still, there is always the possibility that your carrot planting will be afflicted by any one of a number of carrot pathogens. A comprehensive look at carrot pathogens is beyond the scope of this article, but it's important to have familiarity with the pathogens that are most likely to become an issue.
The next step is proper diagnosis of a carrot disease — before you implement a management strategy. For assistance with this, turn to your local cooperative extension agency, agricultural university, or ministries of agriculture, which are staffed by experts the grower can call upon for assistance in identification and management, should the need arise.
Here is a overview of the more common carrot pests and diseases.