- SDS is a frequent disease of soybean, but it does not reduce yields every year—suggesting that ILeVO will be used as insurance-based management.
- Using ILeVO increased yields in all 7 on-farm trials in the 2016 growing season.
- The average yield increase across all 7 trials was 7.8 bu/ac resulting in net returns of $63/acre (Figure 1).
- The economic optimum seeding rate averaged across these particular 7 locations was 127,000 seeds/ac, but seeding up to 140,000 only reduced partial profits by $2/ac—so it seems that over seeding is still cheap insurance against conditions that can significantly reduce stands.
Average soybean yield for plots treated with base fungicide+Insectcide seed treatments and base fungcide+insecticide+ILeVO seed treatments at 7 on-farm sites in Illinois and Iowa in the growing season of 2016.
Sudden Death Syndrome (SDS) is a fungal root rot of soybeans that can routinely cause reduced soybean yields in the U.S. Midwest. Soybeans are most susceptible to SDS within a few weeks after planting, presumably because it is easier for the SDS pathogen to penetrate young succulent root tissue vs. older root tissue that has had time to develop more ridged, less penetrable cortical tissue. Given this early season susceptibility, crop scientists have been searching for a seed-applied fungicide that controls the SDS pathogen.
Since about 2012, Bayer CropScience has been testing a seed-applied fungicide (a.i. fluopyram) that shows promise at reducing soybean SDS infection and yield losses associated with this disease. This seed-applied fungicide, as of the 2015 crop season, has been sold commercially under the trade name ILeVO. In addition to controlling SDS, the ILeVO that is treating the plants has also been shown to have fewer soybean cyst nematodes (SCN) per gram of root than plants with no ILeVO treating (Zaworski, 2014), and is currently being labelled for control of SCN.
Given that ILeVO controls SDS and SCN, this new seed treatment could dramatically increase soybean yields and provide significant financial benefits to Midwestern farmers when these diseases are at high enough levels to reduce yields. Since it is not always known, however, if these diseases will reduce yields at planting, ILeVO may be viewed as insurance-based management in the event that these diseases do reduce yields.
Another insurance policy that farmers have used over the decades is to plant more soybean seeds than necessary to produce maximum economic returns. Over seeding provides insurance against significant stand loss that can often occur from poor planting conditions or wet, cold soils that may materialize soon after planting. Recent research, however, shows that soybean economic optimum seeding rates (EOSR) may be as low as 100,500 seeds per acre when fungicide and insecticide seed treatments are used (Gasper et al., 2015), and is well below the current seeding rates that most Midwestern farmers use on their production acres.
Presented with the aforementioned information, it is possible that farmers may be able to reduce their current seeding rates in an effort to help pay for the added cost of the ILeVO ($10-to-$13/140k unit) seed treatment, in effect, trading dollars spent on an over seeding insurance policy for insurance against SDS and SCN.
To help answer these important economic questions, Liqui-Grow implemented some experiments in the 2016 growing seasons to investigate if the EOSR in on-farm trials is as low as some recent research suggests (100,500 seeds/acre), and to see how often buying an insurance policy against SDS and SCN (ILeVO) pays off.
The Applied Questions
- Is the EOSR as low as 100,500 seeds/acre in on-farm trials, and is the EOSR different for seeds treated with base fungicides+insecticide vs. base fungicides+insecticide+ILeVO?
- How often does ILeVO increase yields, and is the yield increase large enough to pay for the added cost of the ILeVO seed treatment?
How Were the Applied Questions Answered?
Four on-farm studies were implemented in eastern, IA and 3 in northern, IL. At each of these sites farmer cooperators seeded soybean at 50,000-to-150,000 seeds/acre in 25,000 seed increments. Half of each of these seeding rate plots were treated with base fungicides+an insecticide seed treatment. The remaining half of each of these seeding rate plots were treated with base fungicides+an insecticide+ILeVo seed treatments.
Plot widths ranged from 30-to-80 ft wide, and plot lengths ranged from 230-to-2,260 ft long. All sites were productive prairie-derived mollisols except for the Peoria, IL site; this site had sandy loam soils and was irrigated.
Calculating the EOSR
For calculating the EOSR, it was assumed that the seed cost was $82/140k unit for the base fungicides+insecticide treated seeds and $96/140k unit for the base fungicides+insecticide+ILeVo treated seeds. It was also assumed that farmers received $10 for each bushel of soybean sold.
All varieties used in these studies were Credenz brand soybeans marketed and sold by Bayer CropScience, and they had average to above average SDS tolerance ratings.
At 6 of the 7 sites, SDS symptoms—chlorotic mottling and leaf chlorosis—were present during the seed-filing period (R6), and these symptoms were almost always more severe in the control plots that did not have seeds treated with ILeVO (Picture 1).
Averaged across seeding rates, yield increases for the ILeVO treated seeds ranged from 3.2-to-15.4 bu/acre (Table 1). Moreover, sites that had more severe SDS symptoms during the seed-filling period tended to have larger yield increases from adding ILeVO to the base fungicides+insecticide seed treatment package. An exception to this was the Clear Lake, IA site. At this site no SDS symptoms were visible during the seed-filling period, but on average ILeVO increased yields 5 bu/acre.
The EOSR for the base fungicides+insecticide seed treatments was 126,000 seeds/acre and the EOSR for the base fungicides+insecticide+ILeVO seed treatments was 128,000 seeds/acre averaged over the 7 sites (Figure 2). Moreover, the EOSR in these studies was about 25,000 seeds/acre higher than what the most recent published research suggests (Gasper et al., 2015).
|Location||Fung+Insectcide||Fung+Ins+ILeVO||Yield Increase||Net Return|
|– – – – – – – – Grain Yield bu/ac – – – – – – – –||$/ac|
|Clear Lake, IA||78.1||83.1||5.0||36.2|
|West Liberty, IA||48.4||53.2||4.8||34.1|
Soybean yields and net returns from using base fungcide+Insectcide or base fungcide+Insectcide+ILeVO seed treatments at 7 Illinois and Iowa locations in the growing season of 2016.
Averaged across these 7 sites, adding ILeVO to a base fungicide+Insectcide seed treatment package increased yields 7.8 bu/acre and economic returns $63.1/acre. This suggests that ILeVO may be a worthwhile insurance policy for farmers to purchase.
Even though there is not a guarantee that ILeVO will provide a return on investment in every season’s yield, increases such as these in 2016 suggest that ILeVO could be bought for the next 5 growing seasons and net returns would still be north of break even.
That being said, the odds are high SDS will return again in one or several of the next 5 growing seasons. While this specific data set does show that the EOSR is around 127,000 seeds/acre—still lower than the avg farmer seeding rate—it still may be a wise insurance policy to seed closer to 140,000 seeds/acre, given it is difficult to predict when significant stand loss will occur, and seeding 140,000 vs. 127,000 seeds/acre only lowered partial profits by $2 per acre in these studies.
- Gasper, A.P., P.D. Mitchell, and S.P. Conley. 2015. Economic Risk and profitability of soybean fungicide and insecticide seed treatments at reduced seeding rates. Crop Sci. 55:924-933. https://dl.sciencesocieties.org/publications/cs/pdfs/55/2/924 (accessed on 21 of Dec 2016).
- Zaworski, E.R. 2014. Effects of ILeVO® on soybean sudden death syndrome and soybean cyst nematode. Master’s Thesis, Iowa State Univ. http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=5268&context=etd (accessed on 21 Dec 2016)