You can control sweet potato soil pox by making your soil slightly acid with sulfur applications. Remember that certain other crops don't do well on acid soil nor is this practical for soils that already have been heavily limed.
Hooker, W. J. and Peterson, Lewis E.
"Controlling Soil Pox in Sweet Potatoes,"
Iowa Farm Science: Vol. 7
, Article 8.
Available at: https://lib.dr.iastate.edu/farmscience/vol7/iss8/8