UNITED States of America’s grain farmers scrambled to find shelter for their crops and handlers hunted for alternative transportation routes, as widespread floods shut waterways from Illinois to Missouri and spurred a surge in physical prices of corn and soybeans.

The sudden jump in prices could complicate a months-long stand-off between farmers who are unwilling to sell their bumper crop at low prices and buyers who have refused to budge on their cash offers amid plentiful supplies.

It could also further curb export demand, with U.S. traders struggling to compete with their cheaper Latin American rivals.

Cash premiums for soybeans GRYM in the U.S. barge market, jumped to as high as 70 cents per bushel on Wednesday, their loftiest since mid-November as the rapidly rising waters forced the Coast Guard to shut a five-mile section of the Mississippi River, including the harbor at St. Louis, traders told Reuters.

Surcharges for corn GRYN hit 49 cents on Wednesday, up almost a third from 37 cents a week ago and the highest in nearly three weeks. Premiums are paid on top of the benchmark futures prices for physical delivery.

Fear of flooded fields and soggy grain piles had some farmers rushing to sell their grains to local buyers, or deciding it would be worth the monthly fees to move it off their farms and store it at grain elevators with bins built on higher ground.

Some grain elevators in southeastern Missouri and southwestern Illinois were having a tough time keeping up with truck traffic this week, according to farmer tweets.