ASX-listed food and agribusiness companies face more drought-related headwinds after Grain Producers Australia warned the latest official forecast for the nation's winter crop is over optimistic and may be out by millions of tonnes.

Commonwealth government forecaster ABARES said on Tuesday that Australia was expected to produce a winter crop of 33.2 million tonnes, including 19.1 million tonnes of wheat, and at the same time warned of a production plunge of more than 40 per cent in irrigated summer crops like cotton.