I just got off the phone with a guy who worked in fumigation for DOW. His advice is to rotate the crop and plant N hybrids. He said that once they are there - it's too late. He now works at that business that the master gardener reminded me of. So, he would have tried to sell me something if there was anything that would at least halfway work. (No stars)
He also agreed with Marsha that solarizing only lasts up to 3 months.