This year’s soggy weather in many locations has set the stage for future foliar diseases this growing season. Mark Carlton, an Iowa State University Extension agronomist, outlined the situation in Iowa at the ISU Southeast Iowa Research Farm near Crawfordsville, earlier this month.

Soybeans

In soybeans, watch for these foliar diseases: 

1.    Brown spot

2.    Frogeye leaf spot

3.    Cerospora leaf spot

Fungicides can help protect soybeans from these diseases. However, there are no thresholds developed. Start scouting at R1 (beginning flowering) and watch for disease movement and rainy cold weather. These factors can increase the odds of a positive payback from fungicides. Carlton notes there were cases last year where timely fungicide applications at R3 (beginning pod) had an 8 to 10 bushel per acre payoff.

Fields with continuous no-till beans, particularly with frogeye leafspot, also favor disease development.

Corn

In corn, the decision is more clear-cut. “We need to get out in the fields and scout,” he says. When corn is at the V14 to V15 stage, when corn is up around eye height, scout up to tasseling.”