From the worst floods in the Midwest grain belt in 15 years to drought in California, damage to crops from inclement weather has topped $8 billion so far this year, the largest US farm group said.

The damage could rise or contract, depending on weather conditions for the rest of the growing season in the United States, the world's top exporter of corn, soybeans and wheat, the American Farm Bureau Federation said.

The flood damage in the Midwest over the past two weeks has lifted prices for US corn, used for food, renewable fuel ethanol and animal feed, to a record high above $7 a bushel, up about 85 percent since the end of 2006 as of Wednesday.

The AFBF said leading farm state Iowa accounted for about half of the damage. "Wet weather and flooding create issues, as farmers are unable to plant their crops," said AFBF senior economist Terry Francl.

"The crops they do plant do not sprout and grow, resulting in few acres harvest."    

"Additionally, the difficult growing conditions greatly reduce the yield of the crop that is harvested," he added. Francl said he expected Iowa corn yields could fall by 16 percent this year and that 1.5 million to 2 million acres of corn and soybeans in the state that farmers intended to plant this spring will likely remain fallow.

AFBF said this would result in an estimated loss of $4 billion to Iowa's crops, and that other states taking a hit from excessive wet weather and flooding are Illinois with $1.3 billion, Missouri $900 million, Indiana $500 million and Nebraska $500 million.

It said an additional $1 billion in losses were expected in other states where conditions remained wet. The US Agriculture Department will provide some insight into the extent of crop damage from the floods when it issues its report Monday on how many acres farmers will plant with major crops, including corn and soy, this year.

The AFBF said some states were experiencing dry weather, with drought taking a toll in several Western and Southeastern states. It said northern California battled the driest spring in its history, and as a whole the state suffered $500 million in estimated damage.

AFBF said on a national basis, the corn yield is likely to decline some eight to 10 bushels per acre from the 2008 trend line, mostly due to inclement weather.

The national soybean average yield is also likely to be down one to two bushels per acre from the current US Agriculture Department projection of 42 bushels per acre.

AFBF said the damage estimate is based on the assumption that weather conditions will be normal for the remainder of the growing season, adding that varying weather conditions later in the season could cause the estimate to grow or contract. - Reuters