Wheat production in the US's most important producing state will slide by 23m bushels this year as disease, insects and frost take their toll, experts have said.

A tour by more than 50 officials, including farmers, academics and representatives from buyers such as General Mills, has estimated wheat production from the state of Kansas at 333.3m bushels this year.

In 2008, Kansas's wheat harvest hit 356m bushels, according to US Department of Agriculture Officials, below the 379.1m forecast by last year's crop tour.

Officials said that this year's lower estimate reflected a yield pegged at 40.8 bushels per acre, down from their 43.3 bushels-per-acre forecast a year ago.

The yield figure is, nonetheless, higher than the 40.0 bushels per acre the USDA estimated for Kansas in 2008.

Disease, bugs and frost

Experts on Wednesday, the second of three days, noted problems with "barley yellow dwarf, wheat streak mosaic, hail damage, Russian wheat aphids, drought stress, wheat mites, standing water in some fields and frost damage", a statement by the Kansas City Board of Trade, which participated in the tour, said.

Yields appeared particularly depressed in the south and west of the state, which typically outpaces North Dakota as America's biggest wheat producer.

However, Kansas's wheat is, effectively, all of the hard red winter wheat variety, of which it is by far the biggest producer, and which is struggling in many other growing states.

A shortage of rain, followed by late frost, has left 75% of Texas's crop, and 70% of Oklahoma's, rated either poor or very poor by the USDA.

The Oklahoma Wheat Commission earlier this week estimated the state's production at 77.4m bushels at a yield of 20.3 bushels per acre.

Oklahoma's production last year was 166.5m bushels on a yield of 37.0 bushels per acre.