German chemical giant Bayer is to appeal against a Missouri court's award of $265m (£203m) to a US peach grower who blamed a herbicide for crop damage.
Farmer Bill Bader sued Bayer and BASF, alleging that dicamba weedkiller drifted onto his orchard from nearby fields, destroying them.
It is the first ruling in some 140 US cases against dicamba, a herbicide blamed for extensive crop damage.
Bayer says its herbicides pose no unreasonable risk if used correctly.
The US agrochemical giant Monsanto, bought by Bayer for $63bn in 2018, sells dicamba-based herbicide and a similar, much-criticised product, Roundup.
US lawsuits against Monsanto's weedkillers may cost Bayer billions of dollars in damages.
It is not yet clear how Bayer and BASF may share the cost of the Missouri damages.
BASF said it would "use all available legal resources" to fight Saturday's ruling by a federal district court in Cape Girardeau, Missouri.
The firms were ordered to pay Mr Bader $15m in actual damages and $250m in fines. He argued that his 1,000-acre (405-hectare) orchard was destroyed by dicamba.
In a statement on Monday, Bayer said it "clearly disagrees with the jury's verdict and is very disappointed".
"We will swiftly appeal the decision. While we have great empathy for any farmer who suffers from crop losses, in the case of Mr Bader there was no competent evidence presented which showed that Monsanto's products were present on his farm and were responsible for his losses."
Dicamba-based herbicides have been blamed for damage to thousands of hectares of crops in US Midwestern states.
In November 2018 the US Environmental Protection Agency (EPA) imposed restrictions on dicamba use, because of the farmers' concerns.
Bayer insists that Monsanto herbicides are safe and "valuable tools for growers". The herbicides "do not pose any unreasonable risk of off-target movement when used according to label directions", the firm says.