Part of the Navajo Nation's potato crop had to be destroyed because of improper herbicide spraying, tribal officials said. Apparently none of the poisoned potatoes went to market. "As far as we know, there's no evidence of (contaminated potatoes) going out to market," said Calvert Curley, director of the Navajo Environmental Protection Agency's Air and Toxics Department. The destroyed spuds were contained on 400 acres sprayed with Dow Elanco herbicide, called "Stinger," before the 18-month planting interval had elapsed. Labeling instructions said 18 months had to pass between any Stinger application and planting. The 400 acres of contaminated potatoes, planted by the Navajo Agricultural Products Industry, had to be plowed under, Curley said. Nine other fields may have been subjected to Stinger treatments, he said, but potatoes stored in a warehouse and cleared for market were not contaminated. The investigation continues, he said. Misapplied herbicide is a violation of the Federal Insecticide, Fungicide and Rodenticide Act. "We do look at it as a violation. ... We want to make sure our laws are being complied with," Curley said. The investigation was conducted by the Navajo EPA, the U.S. EPA's Region 9 office in San Francisco and the U.S. Food and Drug Administration.