Posts tagged ‘Anne Dorrance’

Soybean Rust – Close to Ohio in 2009 but no Cigar

Dr. Anne Dorrane, OSU Extension Pathologist, recently discussed how close soybean rust came to Ohio in 2009. Excerpted from the January 12, 2010 CORN Newsletter:

Soybean rust was a big topic again at the end of 2009. First detections in Kentucky were in early September and followed a month later on late planted soybeans in Southern Indiana. What was most impressive this year – was the amount of rust that built up in the southern states at the end of the season. A limited number of Mississippi producers had yield losses directly due to soybean rust based on reports from Dr. Tom Allen, their field crop pathologist. In addition to the soybean, the amount of kudzu that was also infected is also becoming an issue. The good news is that again, not all kudzu is susceptible to the current strains of soybean rust we have right now. And the kudzu patches that are Susceptible are getting placed on maps to make the scouting easier in the future.

The biggest announcement that was made at the 2010 APS National Soybean Rust Meeting held in December was that the sentinel plot system would change. And this is a good thing. We know more, we can be more efficient at scouting now that we know where to look and those of us in the north can get better and knowing when to look. There is no point in searching in Ohio, if the southern states are negative. For 2010, we will again be monitoring the maps and commentary from our southern colleagues at the Soybean Rust website (http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi). We will continue to monitor in Ohio as soybean rust continues to approach the middle tier of states. Hopefully it will continue to miss us or arrive to late to have an impact.

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January 20, 2010 at 8:15 am

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:

August 12, 2009 at 8:10 am


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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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