Chairman Frank Atlee III said the company’s board of directors accepted the resignation of Verfaillie, who had worked at Monsanto for 26 years. Atlee will be interim CEO until a successor to Verfaillie can be found.

“I want to be certain that the shareholders of Monsanto understand that Hendrik’s resignation was mutual,” said Atlee. “Hendrik and the board agreed that the company’s performance during the past two years has been disappointing.”

Atlee also said the board members support Monsanto’s business strategy, and there was no impropriety in Verfaillie’s decision to resign.

Monsanto’s stock fell $1.19 per share and closed at $19.02 following the announcement on Dec. 18.

Verfaillie led the company through a merger with Pharmacia & Upjohn, a subsequent initial public offering and the complete spin-off from Pharmacia Corp., which took place earlier this year.