Shares in German chemicals and pharmaceuticals giant Bayer fell sharply on Thursday, on media reports of new legal risks stemming from its acquisition of US seeds and pesticides maker Monsanto.
Bayer's share price was down 5.3% at €76.50 by 11:00 in Frankfurt, its lowest level since March 2013.
The drop followed a report in German business weekly Wirtschaftswoche that farmers in US states Arkansas and South Dakota were suing Monsanto for damages related to weedkiller Dicamba.
The herbicide is compatible with many of the St Louis-based firm's genetically-modified seeds, but the growers say it harmed other crops on neighbouring fields.
Adding to Bayer's woes, the magazine also reported Brazilian authorities could slap a blanket ban on glyphosate, the main ingredient of Monsanto's blockbuster weedkiller Roundup, from September 3.
The firm did not immediately respond to a request for comment from AFP.
Bayer shares fell even more dramatically on Monday after a US jury ordered it to pay almost $290m in damages to a dying California groundskeeper who said Roundup had caused his cancer.
Executives insist that scientific studies prove the Monsanto product is safe, but investors fear courts could reach similar findings in thousands of pending American lawsuits.
On top of the risk that some analysts see of Bayer having to pay out up to $10bn in damages, the ruling could add to glyphosate's bad reputation in many countries and harm sales.
The European Union last year renewed the chemical's license for five years rather than the usual 15 after intense campaigning by environmentalists, with some members like France and Germany planning to limit glyphosate use or ban it altogether.
Bayer's share price has lost nearly 18% in value this week, wiping billions off its market capitalisation.* Sign up to Fin24's top news in your inbox: SUBSCRIBE TO FIN24 NEWSLETTER