You should know at least the basic knowledge of trading. Preferably, one should have at least any background from an economics in order to understand the market better as compared to the ones who does not have. Though it is not required for one to have such background, it is preferred as it may result to better results and for risk avoidance. But the primary factor here to consider is the experience of the trader on his field since it hones their talent and skills through the years of working on the actual scenario.
I have some friends who do not have any background with a business/economics degree but they earn large amounts of cash and are also experts on their field.