After a phoned-in threat from someone in Iowa, the U.S.D.A. has pulled its staff from an annual tour of Midwest farm fields that develops yield estimates.

According to a report from Reuters, “an angry farmer” called in the threat against a U.S.D.A. official who was on the privately-organized ProFarmer tour.

Farmers have been upset with the higher-than-expected official yield estimates released by the U.S.D.A. 10 days ago, as corn prices fell dramatically on the news. The Trump Administration’s decision on August 9th that granted ethanol waivers to big oil companies has fueled frustration in farm country, too.

A spokesman for Farm Journal, the parent company of ProFarmer, said “this is clearly a stressful time” and precautions have been taken to ensure the safety of those who will participate on the tour’s final leg today.  That final leg starts in the Spencer area.

A statement posted on the ProFarmer website indicates the threat came “from a person in Iowa who was not affiliated with the event.” The annual Pro-Farmer tour, in its 27th year, features scouts taking day-time tours of fields along with evening meetings with local farmers. Things reportedly got heated at the tour stop in Grand Island, Nebraska earlier this week and police at the next stop in Nebraska City were dispatched to the tour’s evening event there on Wednesday. The tour wraps up in Rochester, Minnesota tonight.