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Research Highlights
Asian Soybean Rust Monitoring System Shows Savings

By Barb Baylor Anderson

While direct economic loss from Asian Soybean Rust (ASR) has been minimal in South Carolina in the past, recommendations to not spray a foliar fungicide late in the growing season have saved farmers an average $15 per acre per year. The ASR monitoring system being developed with funding from the South Carolina Soybean Board can help save costs and prevent yield loss.

“Since we have been surveying for ASR, we estimate our recommendations have saved at least one foliar fungicide application across 75 percent of the state’s soybean acres per year. That is nearly $4 million per year in savings,” says Jonathan Croft, Clemson University Extension agent and principal investigator for the checkoff study. “Early detection allows for properly timed fungicide applications to prevent yield losses. And if ASR is not detected by the monitoring system, farmers can save the cost of a fungicide application for ASR control.”

The monitoring project, which has been stationed in the southwestern part of South Carolina, can identify when ASR is present and give farmers ample time to make management decisions that will help preserve profitability. Several sites in the region are sampled August 1-October 15 with results and recommendations reported to farmers and their agronomy partners each week.

“In 2019, we learned that even with an extreme drought, ASR was able to establish in South Carolina soybean fields after we received rainfall from tropical systems that passed over the state. Since the detection was late in the growing season and extreme drought had already reduced soybean yield potential, no fungicides were recommended for ASR control,” says Croft.

Croft cautions that they have learned ASR can establish even in extremely hot dry years with occasion rains. So, they focus sampling on field edges that maintain dew well into the morning.

“We can use early planted fields to monitor for ASR since we have been successful finding ASR at very low levels,” he says. “There has been no need to plant specific ASR monitoring sites earlier than our earliest farmer planted fields. Moisture and temperature have to be just right for significant ASR spread, and we have not seen that combination here for some years now.” 

Croft adds that even though ASR is the focus, they do scout for other diseases and insects and keep soybean farmers well informed on issues coming their way. Farmers who wish to be added to the weekly email update distribution list can contact him at Croft@clemson.edu.

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.