With some soybeans in Indiana blooming and setting pods while others are in early vegetative stages, a Purdue Extension agronomist says growers should be making crop management decisions based on plants' development.

One of the first steps in preparing a strategy is to examine how the conditions in which they were planted have affected the plants.

"Some farmers basically have two or three separate crops in the field," said Shaun Casteel. "Soybeans planted in wet soil may be experiencing complications from sidewall compaction."

When the soil hardens and dries, underdeveloped roots may curl upward, and the plants might not receive enough nutrients and show signs of deficiencies. A foliar nutrient application early in the growth could temporarily alleviate problems until rain stimulates roots to grow and penetrate the compacted layer, Casteel said.

For beans in the reproductive growth stages where the bloom and pod are set, farmers should scout plants for soybean aphids. Casteel recommends spraying an insecticide for more than 250 aphids per plant during these growth stages.

The insects that typically attack more mature plants might cause problems for late-planted beans.

"There might be a stronger wave hitting the late-developing soybeans if aphids increase their population in the more advanced soybean plants, especially if they have some beans that are behind, farmers should pay attention to the aphids now," Casteel said.

Soybeans should be scouted for diseases like Septoria brown spot and Frogeye leaf spot to determine if a fungicide application is warranted during pod set, Casteel said.

"There isn't a defined threshold for these diseases; you have to look at the current severity and the potential for more damage based on growing conditions, as temperature and humidity levels vary based on the disease of concern. But research is showing that a fungicide application provides yield protection and a return on investment if the diseases are present," he said. "Fungicides should be a management strategy based on scouting and disease pressure, not a prophylactic one."

Casteel recommends that farmers go into their fields to routinely monitor insect and disease pressures for in-season applications.

"If you see some pockets that are weaker than others, you can find out why and hopefully prevent that in the coming years as well," Casteel said.

Source: AgAnswers