A week’s worth of showers and unseasonably cool weather in mid-April will put Iowa’s earliest-planted corn at greater risk of seedling diseases like pythium, according to plant pathologists.

"Pythium loves wet, cold soils," said Alison Robertson, Iowa State University Extension field crops pathologist.

That was exactly the kind of weather that bogged down Iowa planters from April 18-25. Only 14 percent of Iowa’s corn was planted before April 26, 10 points behind the five-year average, ac­­cording to the Iowa Department of Agriculture’s weekly crop pro­gress report. The planting pace picked up significantly last...