The U.S. Department of Agriculture has refused to pay claims filed by two Idaho families who contend its pesticide treatment contaminated their crops and poisoned a cattle herd. Instead, USDA told the families to file a lawsuit — a costly endeavor that could bankrupt the farms and risk the $70 million potato pest eradication program in Idaho. The Potato Cyst Nematode (PCN) was discovered in 2006, threatening Idaho’s $900 million potato industry. The next year, the USDA began treating infected fields with methyl bromide. The treatment reduced the pest, but it was stopped in 2014 because of concerns from a...