This link can be of some help because they do outline some good practices. Keep in mind that most of the inseciticides listed at the end are Resticted Use Pesticides that require a license to purchase and apply.

Here is a link that might be useful: Sweet Potato Pests

I've found that most soilborne pests can be controlled with beneficial nematodes applied in the autumn while the soil temperature is still high 4-6 weeks prior to the first frost. I had a breakout of cucumber beetles and these have been reduced considerably. There are several types of nemotodes. The Heterorhabditis bacteriophora is best for the sweet potato and can be purchased online.