growing potatos and sweet potatos white grub control
White grubs are the larva of several beetle species (June Bugs, Rose Chafers, Japanese Beetles and others). Controlling them is difficult since the adults are extremely mobile. See http://cropwatch.unl.edu/web/potato/whitegrub_sandchafer for information on life cycles. There are some products that have some control but all require a license to purchase. There are products to control adults but controlling adults will not solve the grub problem. If they are Japanese Beetle grubs the best control for your situation might be Milky Spore (http://en.wikipedia.org/wiki/Milky_spore). MS is a bacterial disease that affects only JB and can be used on your lawn as well. It will not decrease the number of adults you see since they will fly in from other areas.
Generally what happens is that these grubs are a problem for a few years until various biological controls (other insects, diseases, nematodes, etc.) find them and then their numbers go down and they settle into being a minor problem.
Hope this helps.