KANAWHA | Approximately 50 farmers attended the recent Fall Field Day, at the Iowa State University Northern Research and Demonstration Farm, to learn about crop development and how to deal with insects and late-season plant diseases.

Alison Robertson, ISU Extension plant pathologist, talked about "the disease triangle."

For crop disease to be present, you need three things: a host, a pathogen and the right environment, she said.

There's not much producers can do about environmental conditions such as temperature and moisture, but it does help to do certain things like plant wider rows to prevent white mold in soybeans, according to Robinson.

The most important thing to do is to rotate crops in a way that "takes the host out of the equation," she said.

This means tracking which diseases show up in which fields each year so in the future soybeans aren't planted in ground with a history of soybean diseases and corn isn't planted in fields with a history of corn diseases, according to Robinson.

Gray leaf spot has been the most prevalent disease in corn this season, she said.

Farmers asked Robinson about other diseases they are concerned about, including bacterial leaf streak.

She said bacterial leaf streak has been reported in eight states, including three counties in Iowa: Crawford, Dubuque and Emmet.

Robinson said bacterial leaf streak tends to be more common in areas where corn is irrigated.

She also said the disease actually was more widespread in Iowa last year than this year. 

Because it's a bacterial disease, it needs to be sprayed with an antibiotic, not a fungicide, Robinson said.

She also told the farmers that for any blight on crops, they should not use a fungicide until they determine it if is a fungal disease.

Sudden death syndrome in soybeans is usually more prevalent in southern Iowa, but has also been reported in the northern part of the state this year, according to Robinson. She said it is more likely to be found in end rows.

Robinson said there's also been a lot of downy mildew in soybeans, but she doesn't think it will hurt yields. 

She advised farmers to scout their corn fields for ear and stalk rot. If more than than 10 percent of the plants have rot, an earlier harvest should be scheduled, according to Robinson.

Other speakers at the field day were Mark Schnabel, Northern Research Farm superintendent; Erin Hodgson, ISU Extension and Outreach entomologist; Mark Licht and Sotirios Archontoulis, Extension cropping systems specialists; and Paul Kassel and Angie Rieck-Hinz, Extension field agronomists.