US apple growers are counting the cost after a severe frost earlier in the year killed off most of Iowa’s annual crop.

The impact of the late frost, during the first three days of May, could mean that some Iowa apple orchards will not open at all this autumn, or will close prematurely.

The orchards were experiencing one of the most prolific blooms since the late 1980s following warm weather conditions in late April, but temperatures in the low 20s at the beginning of May froze blooms and turned them brown.

One producer said: “It was sickening. The trees were full of blooms and they just froze right off. They got hammered. You walk down the rows and there's nothing there.

Some farms have lost 90 per cent of their fruit, following the chill, and will mean severe financial losses for the sector.