Source: Iowa State University Extension

Although Iowa has had a good planting season, cooler and slightly wetter conditions in May could lead to increased risk for certain crop diseases, according to Iowa State University Extension.

Seedling damping off will be a disease to watch for as it likes a cool and wet planting season. The most common diseases in a cool planting season are Pythium damping off and Fusarium root rot. If replanting has to be done because of frost damage or diseases, fungicide treated seeds should be used because the risk of seedling diseases will be higher, especially in fields that had diseases. 

Original press release