Sclerotinia is a pretty common fungal pathogen and many kinds of vegetable and forage crops are susceptible including brassica sp. common to wildlife food plots like chickory, turnip, rapes ect. It is usually a concern for large-scale vegetable growers and canola (oilseed rape in the north), and sugarbeet farmers. Normally, they are using fungicides to control in these situations but there are some rotational cropping strategies that have been known to minimize the infestations.
Problem is that it is persistent in the soil for quite a few years. Fungicides are only preventative and not curative so if you already have it, its too late to apply a fungicide to help, save for maybe minimizing some spread to some unaffected areas or tissue. Fungicides also will have no effect on sclerotial bodies that are in your soil, so its not like you can sterilize the soil with these products. Fungicides can be expensive too.. just ask any grower that is using them to save themselves from soybean rust nowadays.
I would say if you havent had a problem with it, you arent likely to. If you have seen it, just ask a local county extension agent what your options are.