Pythium is a disease associated with cool, wet weather. Infection typically occurs in soils with temperatures below 50º Fahrenheit, although some species tolerate warm soil conditions quite well. The Pythium oospore is a swimmer. Free moisture in the soil is required for infection to take place.
Since warm weather has been slow to arrive this spring, and corn planting has been slightly delayed, Pythium may actually be less of a problem this year because soils should now more earnestly warm up and dry out. The same weather and soil conditions are required for Pythium infection to take place in both soybeans and corn, so soybeans could also be spared from significant infection this year.
In corn, initial symptoms of Pythium infection often include pinched or shriveled mesocotyls, or crown infections. First signs of this disease typically include watery discoloration of affected tissue, which later shrivels and turns light brown, to brown in color. As the infection progresses, all affected plant tissue becomes mushy. Corn can sometimes grow away from infection in the mesocotyl if nodal roots have emerged and are functional. Crown infections are usually fatal.
Seed treatments containing mefenoxam or metalaxyl are generally effective in providing temporary protection against Pythium. Watch for ethaboxam, a new seed treatment fungicide, to be commercialized soon.