DowDupont, the chemicals group, has estimated that its earnings fell by a percentage in the “high teens” in the first quarter of the year, hit by flooding in the US midwest and a squeeze on margins in packaging and plastics.

Its previous guidance was that earnings before interest, tax, depreciation and amortisation would drop by a percentage in the low teens.

In after-hours trading the shares were down 2.6 per cent at $51.37.

The warning on earnings comes just a few days before DowDupont, formed in the 2017 merger of Dow Chemical with DuPont, begins its planned break-up. A new Dow, including plastics, petrochemicals and related products, will be spun out on Monday April 1, starting trading the following day. The agriculture business, called Corteva, is scheduled to be spun off in June.

The group identified two main factors hitting earnings in the first three months of 2019. The agriculture business, which makes seeds, pesticides and related chemicals, was hit by the flooding in the midwest, a key US farming region. Transport disruptions halted farming operations and restricted product deliveries, leading to a 4 to 6 per cent drop in sales and a loss of $125m to $150m in ebitda.

Meanwhile in the plastics and packaging division, part of the new Dow, sales have fallen more sharply than the company expected, dropping by a percentage in the low teens rather than the high single digits drop that was projected in January. The division’s ebitda has also dropped more than expected and is set to be about $100m lower than in the previous guidance, as a result primarily of “greater than-expected margin compression globally in packaging and speciality plastics”.

DowDupont said it would give further details, including an assessment of the full year impacts of the floods, with its first-quarter earnings on May 2.