C.O.R.N. Newsletter 2013-02

The Soybean Pathology Program spent a lot of time on the road last summer evaluating different management practices for Ohio’s prominent soybean pathogens.  To be honest, drought conditions are not conducive to most plant pathogens and with the dry weather following planting and the erratic emergence we don’t have a lot to report.  These years are always good to get some baseline data.  We planted 1,676 plots to evaluate material in 39 tests from 10 companies in addition to our own field tests.  These plots spanned 11 field sites across 9 counties in Ohio.

The following is a list of where we did find some differences.

1) Sudden Death Syndrome. This disease is caused by a fungus and some new data from Leonor Leandro at Iowa State University suggests that infections actually occur shortly after planting.  We also know that symptoms and effects of this disease are enhanced when infections occur in the presence of soybean cyst nematode.  We evaluated 148 MG III entries in a field with SCN egg counts ranging from 200 to 2,000 eggs/cup of soil. SDS developed at this location and 60% of the entries developed no symptoms or a trace amount.  This is very encouraging to see that more lines have high levels of resistance to this root pathogen.

2) Soybean cyst nematode – we were able to assess yield differences between SCN resistant and SCN susceptible varieties at one location, where there was a 35% yield difference or loss from planting a susceptible variety. For other locations, all of the varieties were resistant and there were no significant differences among the treatments that we evaluated.  We are still processing fall soil samples from 210 plots - as soon as those are complete we will have more reports.  We planted 876 plots to SCN and SDS tests.

3) Seed treatments for Phytophthora sojae and Pythium spp.  We evaluated 108 different treatments at the Phytophthora field at OARDC Northwest Research Station.  This study, which had 600 plots, received very minor disease pressure.  This is the first year that our cross aisles, which are planted to a super susceptible variety did not all die.  Despite this low disease pressure, we did get a significant difference for seed treatment in one study.  Yield from seed of a susceptible variety, which was treated with ApronXL at 0.64 fl. oz/cwt, had significantly higher yield (9 bu/A) than that of the nontreated. Yields were also significantly different at a second location for seeding rate study, seed treatment, and a variety evaluation. 

4) We also evaluated the efficacy of fungicides towards other soil borne pathogens (Rhizoctonia, Fusarium graminearum); foliar pathogens (frogeye leaf spot) and Sclerotinia stem rot (white mold).  Many of these compounds have not been labeled nor has the final formulation been developed.  Our Sclerotinia field had less than 20% disease – mostly down in the 3% range for both nontreated and treated areas of the field.  Frogeye leaf spot developed in parts of the field with 3 to 18% of the leaf area affected on individual leaves.  Yield loss could be measured in some areas of the field with a 4.5 and 7 bu/A difference between treated and non-treated areas of the field.  All of the fungicides reduced the incidence and severity of frogeye leaf spot.   

All of this would not be possible without the awesome collaborations we have with the OARDC Farm staff at Northwest, Western and here in Wooster as well as the county educators, crop consultants and more importantly the producers who give us access to their “problem” fields.