No. 16 Article 5/July 13, 2007

Foliar Fungicides on Soybean

Several foliar fungicides are now available for use on soybean in Illinois as either a fully registered product or through a Section 18 emergency-use exemption for soybean rust.

The strobilurin fungicides Quadris and Headline were evaluated in soybean trials across Illinois in 2005 and 2006. In 2005, seven of the eight sites had a significant yield response to either Headline or Quadris, compared to the untreated control. (Figure 3.) However, in 2006, only three of the nine sites had a significant yield response, compared to the untreated control. (Figure 4.) The fungicide applications in these trials were made when soybean plants were at the R3 growth stage.


Figure 3. Results of Illinois soybean fungicide trials in 2005. An * means that the fungicide had a significantly greater yield than the untreated control at that location with a 90% level of confidence. (Data courtesy of Wayne Pedersen, University of Illinois.)


Figure 4. Results of Illinois soybean fungicide trials in 2006. An * means that the fungicide had a significantly greater yield than the untreated control at that location with a 90% level of confidence. (Data courtesy of Wayne Pedersen, University of Illinois.)

In other northern states, results have also been inconsistent. Dr. Marty Draper (USDA-CSREES) summarized results of soybean fungicide trials conducted throughout the northern United States (IL, OH, MO, KS, DE, NE, SD, MN, ND) at the 2005 National Soybean Rust Symposium in Nashville. He reported that an economic benefit with the use of Quadris or Headline fungicide was realized only 40% (10/25) and 25% (8/32) of the time, respectively, in these trials (presentation available here).

Foliar soybean diseases that have been reported throughout the state thus far are Septoria brown spot, frogeye leaf spot, downy mildew, bacterial blight, and bacterial pustule. Thus far in 2007, soybean rust has been reported only in Florida, Georgia, Alabama, Louisiana, and Texas. Keep updated on the whereabouts of soybean rust at the Web site.--Carl A. Bradley

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