My potatoes are where the beetles have usually not been a problem. The eggplants, on the other hand, are in a different garden and have been hammered by potato beetles from the get-go!
I had a bottle of Bt tenebrionis, variety san diego around for a number of years. Who knew that this variety of Bt was genetically engineered?!? Well, when the organic standards kicked in, the organic growers kicked Bt san diego out! As a result, the labs stopped making it and I guess, I wouldn't buy it if it was available. It did, however, work at killing the beetles.
There's something new called Spinosad. It is "a naturally occuring soil dwelling bacterium." So, it is like Bt in that regard.
I have been spraying with rotenone/pyrethrum weekly and, altho' it is recommended for the beetles, it doesn't work well. Maybe there are just too many of the critters around that garden and the eggplant are too much of a lure!
Right now, I think that I should have bought the Spinosad early in the season. But, speaking of season . . . shouldn't your Yukon Golds have pretty much lived out their season? Would it be okay for you just to harvest them and go ahead and trample the potato bugs in the processes?
Steve