Update:
We published a manuscript in Plant Disease on the previous two years’ evaluation (2013-2014) of several fungicide products. In the previous two years' evaluation, IleVO seed treatment or in-furrow application was superior to manage SDS than other fungicide products. We continue field experiments in Iowa, Indiana, Michigan, South Dakota, Wisconsin and Ontario, Canada including new fungicide products to compare them with base seed treatment and ILeVO in their ability to reduce SDS. In 2015 and 2016, we evaluated eight fungicide products applying on seed and foliar on SDS susceptible and resistant cultivars. Plant population, root rot, foliar SDS incidence and severity, and yield data were recorded using standard protocols. Root samples have been collected and are being processed to quantify F. virguliforme in soybean root tissue using a qPCR assay identified using our NCSRP project. Data collection from participating states and analysis is on process.

We completed a study evaluating planting date and seed treatment effect on SDS development and published a manuscript in Plant Disease. To summarize, ILeVO seed treatment reduced disease severity and increased yield nearly in all plantings and cultivars, with a maximum yield response up to 21% (Roland Iowa). No clear link between early planting and SDS was observed. Planting earlier than Mid-May did not increase the risk of SDS being developed. Mid-June plantings yielded lower grain up to 19 bu/a compared to early May plantings. In all experiments, early-May plantings resulted in lower or similar FDX as treatments planted in mid-May or early June. We learned from his study that planting should not be delayed for management of SDS.

We completed field experiments on determining how increasing SCN resistance to SCN-resistant cultivars will affect SDS resistance performance. A manuscript entitled “Effect of soybean cyst nematode resistance source and seed treatment on population densities of Heterodera glycines, sudden death syndrome, and yield of soybean” is in review in Plant Disease. From this study, we found PI88788 resistance source has been broken by nematode population in all tested sites except in Rodney, Ontario. SCN resistance played a critical role on SDS development. Cultivars with no resistance SCN had the highest disease and lowest yield. Fall season SCN population density and SDS were positively correlated.

In 2016, we established field experiments at two locations in Iowa and other participating states coordinating with Dr. Shawn Conley to look at the effect of ILeVO on soybeans planted at different planting populations. We collected data on plant population at different growth stages, SDS incidence and severity multiple times, and yield. A manuscript entitled “Response of broad spectrum and target specific seed treatments and seeding rate on soybean seed yield, profitability, and economic risk across diverse environments” has been accepted for publication in crop science. Economic risk and profitability of seed treatments and seeding rate for each seed treatment was also estimated. Three seed treatments with different components and relative cost were used. The three seed treatments consisted of untreated control (UTC), a commercial base fungicide + Insecticide + nematistat seed treatment (CB), and CB treatment + IleVO (fluopyram). Soybean yield was evaluated with and without history of SDS. It was apparent that sites with a history of SDS and visible SDS symptoms benefit the most from the ILeVO treatment.

We established field experiments in Iowa, Indiana, Michigan, and Wisconsin and Ontario to investigate the effect of corn residue on SDS development. We compared two levels of residue removals and two tillage systems in corn and soybean rotation system. The first year of data on plant population, root rot, foliar SDS, and yield were collected. Soil samples for determining SDS and SCN level on soil have been collected and will be processed. Data are being analyzed. Preliminary data analysis showed that plots with no residue removal had greater SDS level than those with residue removed in Iowa.

We continue to present our research reports at professional meetings, on Plant Management Network, many state or province level talks, seminars, media interviews, talk in field days and conferences for farmers and also published in state newsletter articles, 20+ media releases etc. To communicate with researchers, we published two manuscripts, one has been accepted, and one has been submitted recently in peer-reviewed journals. We also had several press releases, including some jointly with NCSRP, based on results from this project. We developed two regional publications through the Crop Protection Network (Scouting for Sudden Death Syndrome on Soybean and Soybean Disease Management: Sudden Death Syndrome). These are linked to the SRII site. We also updated SRII with information from this proposal.

View uploaded report

Fluopyram applied on the seed or in-furrow reduced foliar disease index (FDX) and increased yields compared to the commercial base (CB) seed treatment comprised of prothioconazole+penflufen+metalaxyl and clothianidin+Bacillus firmus. Baseline disease influenced the yield and disease response to fungicide treatments. Yield and disease response to ILeVO treatment was not significant when disease pressure was low and response increased with higher level of disease. Moderately resistant cultivars had less disease than susceptible cultivars indicating that resistant cultivars in combination with fluopyram seed treatment or in-furrow application could provide effective management of SDS. Plant population was reduced by ILeVO treatment in a few locations, however, the reduction did not affect yield, likely because the soybean plant can adjust to available space and produce adequate yield despite a reduction in plant population. The effect of fungicides on severity of sudden death syndrome, plant establishment, and soybean yield was evaluated in Illinois, Indiana, Iowa, Michigan, South Dakota, Wisconsin and Ontario. Two soybean cultivars that differed in susceptibility to SDS were planted in fields with a history of SDS and/or with artificial augmentation of F. virguliforme. A total of 16 fungicide treatments were evaluated in 2013-2014. In 2015 and 2016 total 8 treatments including seed treatment, in-furrow, and foliar application were compared.

Planting in early May does not necessary pose soybeans for greater risk of SDS compared to Mid-May and June plantings, but planting late (middle June) reduced yield significantly regardless of SDS severity. Expression of foliar symptoms of SDS depends upon weather, precipitation, around soybean flowering time than soil temperature at plating. Soil temperature at planting was not linked to SDS development. Yields of plots planted in mid-June were up to 29.8% less than yields of plots planted in early May. A two year study was conducted in Illinois, Indiana, Iowa, and Ontario to determine the effects of planting date, seed treatment, and cultivar on plant population, sudden death syndrome (SDS), and grain yield of soybean. Soybeans were planted from late April to mid-June around 15-day intervals, for a total of three to four plantings per experiment. For each planting date, two cultivars differing in SDS susceptibility were planted with and without fluopyram seed treatment. Of the total 12 experiments, Mid-May plantings resulted in higher disease index in two experiments and early June plantings resulted in three, and the remaining six were not affected by planting date. Root rot was greater in May plantings than June plantings for most experiments. Resistant cultivars had significantly lower disease index than the susceptible cultivar. Fluopyram reduced disease severity and protected against yield reductions caused by SDS in nearly all plantings and cultivars, with a maximum yield response of 17 bu/a. The lack of correlation between early planting date and SDS severity observed in this study indicates that farmers do not have to delay planting in the Midwest to prevent yield loss due to SDS.

Cultivars with no SCN resistance had greater SDS severity, greater post-harvest SCN egg counts (Pf), and lower yields than cultivars with plant introduction (PI) 548402 (Peking) and PI 88788-type of SCN resistance. Cultivars with Peking-type resistance had lower final SCN egg counts than those with PI 888788-type and no SCN resistance. A three-year study was conducted in Illinois, Indiana, Iowa, Michigan, and Ontario, Canada, from 2013 through 2015 to determine the effect of soybean cultivars’ source of soybean cyst nematode resistance on SCN population densities, sudden death syndrome, and yield of soybean. Five cultivars were evaluated with and without fluopyram seed treatment at each location. In two locations with HG type 1.2-, cultivars with Peking-type resistance had greater FDX than cultivars with PI 88788-type. Fluopyram seed treatment reduced SDS and improved yield compared to a base seed treatment but did not affect SCN reproduction and final SCN egg counts. FDX and final SCN egg counts were positively correlated in all three years. Our results indicate that SDS severity may be influenced by SCN population density and HG type, which are important to consider when selecting cultivars for SCN management.

The CB and ILeVO seed treatments increased profit at each grain sale price and across all seeding rates compared to the UTC. It was apparent that sites with a history of SDS and visible SDS symptoms benefit the most from the ILeVO treatment. Profit was calculated as follows: (Yield x Grain Sale Price) – (Seed Price + Seed Treatment Price). Economic risk analysis was applied to the profit curves to quantify the uncertainty of a seed treatment increasing profit when selected in January with no knowledge of spring disease and insect levels. Risk was measured as the break-even probability (the probability of breaking even relative to the base case of UTC at 140,000 seeds/a). At a grain sale price of $8/bu, a seeding rate reduction of the untreated seed to 120,000 seeds/a provided substantial risk benefits (99%), but profit was only increased on average $4/a. In comparison, the same seeding rate reduction for the CB maintained similar risk benefits (93%) but also provided a larger average profit increase ($9/a) with limited downside potential (-$3/a) only 7% of the time. Furthermore, the addition of fluopyram at 120,000 seeds/a improved the risk benefits of CB to an almost identical level as the UTC (98%) and provided considerably greater average profit increases for all outcomes ($14/a). Across all seeding rates and seed treatments, however, the lowest risk (99%) and largest average profit increase for all outcomes ($16/a) was ILeVO at its economically optimal seeding rate of 103,000 seeds/a. When the grain sale price increased to $11/bu, reducing the seeding rate below 120,000 seeds/a for the UTC resulting in profit losses across all outcomes of increasing magnitude as the seeding rate was lowered further. In contrast, CB was able to maintain high break-even probabilities and profit margins down to 100,000 seeds/a, while ILeVO did so down to 80,000 seeds/a. The economically optimal seeding rate, where the maximum average profit can be achieved, was approximately 112,000 seeds/a for the $11/bu grain sale price for both CB and ILeVO.

Foliar disease index was higher in residue not removed treatment than in residue removed for both tilled and no-tilled trials in Iowa but no difference was observed in Indiana and Michigan. Different results were observed in-terms of effect of corn residue in soybean yield across the locations. Soybean was significantly lower in residue not removed treatment in no-tilled trial in Iowa but opposite was true in Indiana. Field trials to test the effect of corn residue on SDS was established in 2015 in Indiana, Iowa, Michigan, South Dakota, and Wisconsin. In 2015, all the plots were planted to corn. In 2016, corn was planted in half of the plots, and soybean in the other half. Corn residue and soil samples were collected prior planting soybean to determine whether corn residue harbors F. virgulifome, and whether F. virgulifome is built up in soil with and without corn residue. Sudden death syndrome foliar disease and yield were recorded. The study will be continued in 2017.