Already in short supply, glyphosate inventories are expected to become even tighter in the coming months after Bayer alerted customers that a problem at one of its raw material suppliers will impact its short-term production capacity.

The supply disruption prompted Bayer to declare “force majeure,” a clause that typically suspends a supplier’s obligations when unforeseeable circumstances prevent it from fulfilling a contract.

“One of our key raw material suppliers experienced a mechanical...