(NAFB.com) – As New World Screwworm continues to pose a threat to the U.S. cattle herd and farm economy, American Farm Bureau President Zippy Duvall sent a letter to USDA urging a continued science-based approach to addressing the threat. The letter urges Ag Secretary Brooke Rollins to keep the southern border closed to cattle imports until it’s clear Mexico is capable of controlling the pest. “To date, the northernmost active case of NWS is only 70 miles from the southern border with Mexico, which is too close for comfort,” Duvall said in the letter. “By trusting the science, USDA can make decisions that ultimately protect the health and economic viability of the U.S. cattle herd.” He also said USDA’s ability to drop sterile flies into the affected area is greatly appreciated, as is Mexico’s willingness to participate in controlling this destructive pest.