I turned over a turnip in my raised bed and noticed a huge spot of white/gray that I originally thought was some kind of fungal infection. I pulled out the turnip and noticed that it looked like the aphids that had been eating the leaves last season (that I thought had moved on from my garden) had made their way to the root system. Thankfully there aren't a lot of plant still left in the vegetable bed and I threw away the turnip plus any dirt that had any patch of white but I'm worried it might infect other vegetables that I plan on planting in spring? Is this something that can be fixed with crop rotation?