DES MOINES, Iowa (AP) -

The cool wet spring has delayed planting for corn farmers but it also has presented a problem for soybean producers.

A soil-borne fungus that thrives in excessively wet years causes a disease known as sudden death syndrome in soybean plants.

It can destroy entire fields or parts of fields. In 2010, Iowa farmers lost about 28 million bushels of soybeans to SDS.

Leonor Leandro, Iowa State University assistant professor of plant pathology, says the key is to plant resistant soybean varieties. She says conditions favoring SDS include compacted soils, soils with poor drainage, and fields with a history SDS.

Leandro says a drier summer will reduce the risk of SDS.

If the plants get into reproductive stages and the weather turns wet, the disease may surface.