food plots are the rage now so aren't sicknesses being spread there
Sickness can always be spread in any herd, the question you are asking is..
"Do foodplots greatly increase the likely hood of spreading disease in wild deer the same way baitpiles do"
The clear answer is no....
Here is great article outlining the biological reasons why the use of foodplotsisnot comparable to baiting..
http://www.whitetailinstitute.com/info/news/aug05/3.html