Posts tagged ‘fungicides’

Two Common Soybean Diseases and Fungicide Recommendations

Observations from my sentinel plot as well as other soybean fields indicate that bacterial blight of soybean is present at low levels in many fields. In Ohio, this disease is not considered yield impacting. Bacterial blight is spread by rain and wind, and favored by cooler weather. Bacterial blight and brown spot are likely to be confused. I took a few quick photos to show the differences.

Bacterial blight symptoms: small, brown lesions that are yellow to brown and often are surrounded by a yellow halo.

One of the most common soybean pathogens in Ohio is brown spot. Brown spot also produces yellow to brown lesions, however, the lesions are typically found in the lower canopy on older leaves and do not have a yellow halo present. (Photo credit: Anne Dorrance)

I had incorrectly identified the symptoms in this image as brown spot. Thanks to John Damicone from Oklahoma State University for correctly pointing out to me that this is NOT brown spot.  The image is of Cercospora blight on soybeans. this symptom is getting some debate right now -- is it Cercospora blight or is it a sunburn type of effect on some varieties.  We have started to a small project to try and identify what this is in response to some samples and feedback from some other regions in the state.

I had incorrectly identified the symptoms in this image as brown spot. Thanks to John Damicone from Oklahoma State University for correctly pointing out to me that this is NOT brown spot. The image is of Cercospora blight on soybeans. This symptom is getting some debate right now, and the question is whether or not this is indeed Cercospora blight or is it a sunburn type of effect on some varieties. Dr. Dorrance has indicated that there is a small project to try and identify what this is in response to some samples and feedback from some other regions in the state.

Key point: Foliar fungicides will protect against brown spot, but are not recommended for management of bacterial blight. Brown spot is considered a minor foliar disease of soybean in Ohio, but yield differences have been documented with fungicide application. OSU research has demonstrated that fungicide applications can reduce the incidence and severity of foliar diseases as well as the minor foliar pathogens found in Ohio. Timing of application is one critical factor in fungicide application. Also, it is important to consider cost-benefit analysis given that a fungicide application may only increase yield by 3 bu/acre.

Full audio podcast available here:

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August 12, 2009 at 8:10 am

Fungicide Use Evaluated, Summarized in Soybeans

In the recent Iowa State University Integrated Crop Management Newsletter, XB Yang and his associates summarize six years of fungicide research on soybeans. Their research appears to be exhaustive, examining up to 50 treatments replicated four times in a year. Obviously, the summary of data relates directly to Iowa, but I believe there is some applicability in Ohio.

Their study found that some soybean fungicide treatments consistently ranked top in terms of increase in yields in our multiple year tests (except for one season) even when disease pressure was low to moderate. Also, they found that application at R1 or earlier did not pay off, but application at R3 consistently produced highest yields. They summarize their study by stating that fungicide application is best reserved for seasons when foliar diseases are severe. The full Iowa State University article is available here.

In local research, Gary Prill and I have conducted three years of similar research at Farm Focus. Our findings are consistent:

2006: We compared separately Quadris, Headline, and Presto (foliar fertilizer) to an untreated check. Fungicide application was made at soybean growth stage R3. The Headline treatment provided a statistically significant yield increase compared to the Quadris, Presto and untreated check. The application of Headline paid for itself and provided an economic return in 2006. Study available here: http://farmfocus.osu.edu/bean_plant_health-06.pdf

2007: We compared separately Stratego, Headline and Presto (foliar fertilizer) to an untreated check. Fungicide application was made at soybean growth stage R3. The Headline treatment provided a statistically significant yield increase compared to the Stratego and untreated check. The application of Headline paid for itself and provided an economic return in 2007. Study available here: http://farmfocus.osu.edu/bean_plant_health-07.pdf

2008: We compared separately Domark, Headline and Stratego to an untreated check. Fungicide application was made at soybean growth stage R3. None of the treatments provided a statistically significant yield increase when compared to the untreated check even though the Headline and Domark treatment increased yield over the check. (Unpublished at the time or writing this blog post)

It is clear from three years of data that using fungicides on soybeans as a preventative measure may provide a net return in some years. In none of the three study years at Farm Focus was soybean foliar leaf disease present at levels that would have justified a fungicide treatment.

Full podcast available here:

12/18/08 Update:

XB Yang contacted me and provided a link to the full presentation.  He indicates the presentation is available for use, except for the photos (which are copyright protected). Full presentation available in a pdf file here.

December 3, 2008 at 7:00 am 2 comments

Common Rust appearing in Corn

Common rust has become prevalent in most corn fields at some levels. So far, I have only found low levels of rust in corn. In this week’s podcast I discuss local implications of common rust on corn based on a recent Purdue Pest & Crop Newsletter.

July 30, 2008 at 7:00 am


Notice

This blog is no longer being maintained. Information on this blog may still be relevant, but for the latest agronomic information and farm management information please visit http://corn.osu.edu and http://ohioagmanager.osu.edu, respectively.

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