Monsanto raised doubts over forecasts of Brazilian corn sowings to set a fresh record next season, flagging the dent to planting prospects from weak values – which in Mato Grosso may soon fall below transport costs to port.
Some commentators see Brazilian corn seedings in 2017-18 maintaining their long-term growth trend, with the US Department of Agriculture forecasting area of a record 17.7m hectares, up 200,000 hectares year on year.
However, Monsanto chief operating officer Brett Begemann noted the dent to the appeal to farmers of corn from prices which were "depressed compared to last year", meaning that the seed giant was expecting farmers to "cut the acreage back a bit.
While the fall was "too early too call" in detailed terms, "we do anticipate it will be down some.
"We're planning for somewhat of a reduction in acres," Mr Begemann said, with Monsanto taking the corn price weakness "into consideration as we look at pricing our genetics", and not expecting a repeat of the strong price rises enjoyed in 2016-17.
The comment come as Brazilian corn prices extending a decline from highs reached last year, when the country was left with tight supplies by a poor harvest following on from a bumper export programme.
According to research institute Cepea, corn prices on Tuesday in Sao Paulo fell to R$25.80 ($7.86) per 60 kilogramme bag, equivalent to $131 per tonne, or $3.33 per bushel.
That is down more than half from a high of R$53.36 per bag reached in June last year.
And in states further away from port, values are substantially lower, depressed by the need to factor in transport costs to port and still compete on export markets.
These states include, notably, Mato Grosso, the top grower of the safrinha crop corn currently being harvested.
In Mato Grosso, the "current price of corn in the state is in the range of R$16.00 per sack or approximately $2.20 per bushel," said Dr Michael Cordonnier at Soybean and Corn Advisor.
Besides being a little below a government guaranteed value of R$16.50 per sack, "the current price is below the cost of production", Mr Cordonnier said.
This factor is likely to be make farmers reluctant to sell their crop, and will, many observers believe, render then less likely to seed corn for 2017-18 as well.
The International Grains Council, which last month cautioned of "low [corn] prices seen deterring some farmers in Brazil, releases fresh estimates on Thursday.
Imea, the Mato Grosso crop institute, estimates that the state's growers have sold 60.5% of their 2016-17 corn, compared with a figure of 84.8% a year ago for the 2015-16 crop.
Imea also highlighted that the price of corn in Mato Grosso had fallen so far that the crop was worth only marginally more than the cost of taking it from the inland state to the Sao Paulo port of Santos.
While in June last year, corn, at R$34.21 per bag, achieved R$18.07 per bag more than the transport cost to port, that gap now has narrowed to R$0.81 per bag.
"The cost to dispose of the cereal may soon be higher than its price," Imea said, terming this "scenario not good".
The dynamics "reinforce the need for improvement" in Brazil's infrastructure for transporting Mato Grosso crops to port.
By Mike Verdin