By Ludwig Burger and Patricia Weiss

FRANKFURT, Nov 15 (Reuters) - Some Bayer BAYGn.DE investors say CEO Bill Anderson should speed up turnaround efforts, including boosting efficiency and drug development, to restore confidence and revive the company's share price that hit 20-year lows after its shock warning this week.

The agriculture and pharma group said on Tuesday that weak farmers' demand would likely translate into lower earnings next year. The warning sparked a 14.5% drop in the German company's shares, which continued a long streak of underperformance largely due to the 2018 takeover of Monsanto.

Anderson has started cutting managerial jobs, speeding up decision-making and slashing red tape to turn around the embattled industrial group, while putting on hold plans to break up its diversified businesses.

But top-20 shareholder Deka Investment said those moves have had little impact on recent results and the outlook.

"The restructuring programme has to have an effect on revenues or costs. Otherwise shareholders' patience with management will be put to a hard test," said Ingo Speich, Deka's head of sustainability and corporate governance.

Some of Bayer's troubles are tied to industry trends such as slumping farmer incomes that are also hitting rivals BASF BASFn.DE and Corteva CTVA.N. But a delay in U.S. approval of a new generation of soy seeds was specific to Bayer and is likely to dent 2025 earnings, its quarterly report showed this week.

Markus Manns, a portfolio manager at mutual funds firm Union Investment, another Bayer shareholder, said Anderson's cost-cutting was the right direction but more needed to be done.

"The next steps need to follow: the strengthening of the pharma pipeline and securing long-term and stable growth," said Manns. He also criticised management for not projecting when the earnings decline would bottom out.

Bayer declined to comment.

Bayer's warning that earnings would likely fall again next year contrasted with an earlier average analyst projection of a 3% increase in 2025 adjusted earnings.

Bayer's $63-billion purchase of U.S. seeds and pesticides maker Monsanto under Anderson's predecessor was a long-term bet on robust growth in farming supplies that has misfired.

Debt and costly U.S. product-liability litigation over disputed claims that Monsanto weedkiller Roundup causes cancer are further burdens Anderson is struggling to shake off.

The CEO vowed on Tuesday the company would do more to contain litigation uncertainty and boost operational performance, on its way to a "bright future".

He pointed to strong launches of the pharmaceutical unit's new drugs, Nubeqa for prostate cancer and Kerendia for kidney disease, but bestselling blood-thinner Xarelto is in decline as it loses patent protection.

Analysts at brokerage BMO Capital Markets said in a note that even though the stock looked attractively valued as a multiple of earnings, no buy recommendation could be given with earnings still contracting.

Bayer's shares trade at 3.9 times estimated forward earnings over the next 12 months, well below BASF at 11.5 and Corteva at 18.7 times, LSEG data shows. The ratio is used to gauge the relative value of stocks and is also a yardstick of profit growth expectations.

(Editing by Rod Nickel)

((ludwig.burger@thomsonreuters.com; +49 30 220133634;))