Prices for top-quality spring wheat have jumped by 90 per cent in the past month and a half, boosted by a scramble by corporate consumers to secure scarce grain and speculative buying by investors.

A surge on Friday in prices for wheat used in bread to an all-time high of $19.88 a bushel – the highest yet paid for any wheat contract and a three-fold increase from a year ago – prompted the US baking industry to call for wheat exports to be curtailed.

The American Bakers Association stopped short of asking for an export moratorium but pressed for curbs on foreign sales. Lee Sanders, ABA vice-president for government relations, said there was usually a surplus in the US wheat market equivalent to three months of US consumption.

“It is currently at a very low one-month level, which is extremely concerning,” she said.

Cereals traders said it was unlikely Washington would support export curtailments, but added that the call highlighted the tightness of the market.

The US is the world’s largest wheat exporter. Faced with strong overseas demand after extreme weather damaged other countries’ crops, its wheat stocks are set to fall to a 60-year low this year.

The shortage of top-quality spring wheat is forcing US millers to consider buying Canadian supplies. Vance Taylor, the general manager at state-owned North Dakota Mill, said his company could buy Canadian wheat for the first time since 1922. “Spring wheat is in very short supply in the US,” he said.

Supplies of lower quality soft wheat, used for baking biscuits and other products, are more plentiful, traders said. In Chicago, soft wheat traded at about $10.25 a bushel.

Rising food prices will be the focus this week of the US department of agriculture annual outlook conference, the main gathering of the industry.

Since last year’s edition, food inflation has surged around the world.

William Lapp, president of Advanced Economic Solutions, a Nebraska-based food consultancy, said that one of the key themes of this year conference would be the realisation that the price surge was not a temporary hump but rather a structural change.

“We are not facing a short-term price blip...but a sustained move to a new and higher plateau for prices,” he added.