Farmers from Iowa to Ukraine are grappling with surging diesel prices and an unsteady supply, forcing them to spend unprecedented sums on fuel in a chaotic market and raising concerns about the autumn harvest.

In the US, where corn and soybean producers are rushing to sow after rains and cold temperatures forced delays, filling a tractor tank daily now costs some farmers $1,000, twice what it was a year ago. And the most intensive part of the farming season is still ahead.