Despite recent improvements in the company's agriculture business and drug development prospects, Bayer shares have been weighed down by legacy litigation woes from the 2018 takeover of Monsanto. But shareholders have also cited a lack of market trust in its top management as a growing burden.

"When it comes to CEO succession we say: the sooner the better," Markus Manns, a portfolio manager at Union Investment, one of Bayer's 10 biggest shareholders, told Reuters.

The demand comes within days of another major German portfolio manager saying that Supervisory Board Chairperson Norbert Winkeljohann must speed up the search for the successor to Baumann, who has led the company for nearly seven years.

"Bayer needs a new strategic positioning, which cannot be credibly accomplished under Werner Baumann," Ingo Speich, head of sustainability and corporate governance at Deka, told the Frankfurter Allgemeine Sonntagszeitung (FAS) newspaper in remarks published on Saturday.

The mutual funds firm is among Bayer's 20 largest shareholders.

Union Investment's Manns cautioned that the non-executive supervisory board may need time to find a qualified candidate.

"I'm sure the board is aware of the urgency of this personnel issue," said Manns.

Baumann, who engineered the troubled Monsanto deal, was given a new contract in 2020 that runs until 2024 and said at the time he would leave the company when that term expires.

A Bayer spokesperson said the company was always open to a constructive dialogue with shareholders and declined to comment further.

($1 = 0.9308 euros)

(Reporting by Ludwig Burger and Patricia Weiss in Frankfurt; Editing by Christoph Steitz and Matthias Williams, Kirsten Donovan)

By Patricia Weiss and Ludwig Burger