Farm and Field

Rust could reach Midwestern soybean crop earlier in growing season

By Herald-Whig
Posted: Oct. 1, 2017 12:01 am

Although Midwestern soybean growers have yet to experience the brunt of soybean rust, growers in the southern United States are very familiar with the disease.

Every year, the fungus slowly moves northward from its winter home in southern Florida and the Gulf Coast states, and eventually reaches Illinois soybean fields -- often just before harvest.

Research shows there is a possibility the disease could jump much longer distances and reach the Midwestern soybean crop earlier in the growing season. Studies suggest that air masses moving from the south could sweep up rust spores from infected plants (kudzu or soybean) and transport them hundreds of miles north earlier in the season, potentially endangering the Midwestern soybean crop.

Although long-distance movement can and does happen, short-distance spore movement has been responsible for most of the annual northward spread of the disease since 2005. It's the short-distance movement that intrigues Glen Hartman, a U.S. Department of Agriculture Agricultural Research Service plant pathologist and professor in the Department of Crop Sciences at the University of Illinois.

In a recent study, Hartman and his colleagues placed two kinds of spore-collecting traps in, around and above rust-infected soybean fields in Alabama, Georgia and Florida. The majority of spores stayed within the canopy, but a proportion (one-third to one-half) floated above. Spores moved laterally away from the field, too, but most stayed within 50 feet, with about half as many moving out to 200 feet. In an average summer, Hartman said, soybean rust rolls up from the south at a rate of about 30 miles a day.

Hartman's study also identifies environmental factors that favor or impede short-distance movement of rust spores. Using a statistical approach known as machine learning, the team found that spores went farther in hot and windy conditions and stayed closer to the canopy in humid, wet conditions.

"What really drives local infection is humidity and moisture," Hartman said. "Those are good conditions for fungal infection and production of spores."

Nutrient loss

The Illinois Nutrient Loss Reduction Strategy is one of many state strategies developed and implemented over the 31-state Mississippi River basin that are intended to improve water quality.

Illinois' science-based strategy provides a framework for reducing both point and non-point nutrient losses to improve the state's overall water quality, as well as that of water leaving Illinois and making its way down the Mississippi River into the Gulf of Mexico.

The Nutrient Loss Reduction Strategy Biennial Report describes actions taken in the state during the last two years along with information from a survey and data from existing sources to serve as a basis to measure progress toward overall water quality improvements now and in the future.

The Agriculture Water Quality Partnership Forum reports that the agricultural sector invested more than $54 million in nutrient loss reduction for research, outreach, implementation and monitoring.

Because of proactive outreach by various agriculture groups, a 2016 survey showed that 70 percent of Illinois farmers already are aware of best management practices to reduce nutrient loss.

In the two years since the strategy's release, significant strides also have been made in limiting the amount of phosphorus discharge from wastewater treatment plants in Illinois.

The report will be updated again in 2019.

"What's made NLRS remarkable is that we had a broad suite of stakeholders that came together to work on the strategy, and they brought not only their ideas, but the support of their organizations. They all got behind it," said Brian Miller, director of the Illinois Water Resources Center. "Working together, we're already starting to see some successes."

Sign up for Email Alerts