Thu, June 15, 2017
By Robert Koch, Field Crop Entomologist, University of Minnesota
We conducted a review of what is known about soybean aphid — in particular, the potential effects on yield and cost-effective management for this pest. We found that in the decade since the establishment of an economic threshold (ET) of 250 aphids per plant for soybean aphid, university-based research has continued to reconfirm the ET and the relationship between aphid populations and crop loss.
We found that although crop and input prices have changed, no consistent economic gain can be found with a reduced ET for soybean aphid. This is because the ET of 250 aphids per plant is already set well below the aphid population level that can cause measurable yield loss.
Fri, June 9, 2017
by Mehdi Kabbage and Damon L. Smith, Soybean Plant Pathologists, University of Wisconsin-Madison
Sclerotinia stem rot (SSR), also known as white mold of soybean, can be a significant yield-limiting disease in the north-central United States. The fungal pathogen, Sclerotinia sclerotiorum
is one of the most successful of all plant pathogens — with an ability to infect over 350 plant species.
With soybean checkoff funds provided by the Wisconsin Soybean Marketing Board, the North Central Soybean Research Program, and the United Soybean Board, as well as the National Science Foundation, we have been able to make significant progress in our understanding of how this pathogen is able to hijack plant defenses and cause disease — and in this process have revealed promising genetic targets for durable host resistance.
Mon, May 22, 2017
by Christian Krupke, Soybean Entomologist, Purdue University
A large, multi-state study confirmed that by the V2 stage, tissue concentrations of thiamethoxam, the neonicotinoid insecticide applied as a coating to soybean seeds, were statistically similar to plants grown from untreated seeds.
We also found that even during aphid infestations, the neonicotinoid seed treatment produced the same yields as using no insecticide at all. The IPM treatment, combining scouting and foliar-applied insecticide where necessary, resulted in significant yield increases.
The relevance of this information for soybean producers is that an IPM approach remains a better pest management investment for the soybean aphid in the North Central region, both in terms of protecting the yield potential of the crop, and in terms of break-even probability for producers.
Mon, May 8, 2017
by Mehdi Kabbage and Damon Smith, Soybean Plant Pathologists, University of Wisconsin
Soybean flowering, apothecia formation, and conducive weather conditions must occur simultaneously for sclerotinia stem rot (white mold) to occur. It is difficult for farmers to assess these factors during the season, and fungicide applications are often ineffective due to poor timing. Fungicide applications might also be unnecessary if the required environmental factors do not converge.
We have made progress on a predictive model to assess the risk of disease development in soybeans. The goal is to help farmers decrease unnecessary fungicide input in low-risk environments and to optimize the timing of application of fungicides in high-risk environments.
Tue, Apr 18, 2017
by Gregory L. Tylka, Soybean Nematologist, Iowa State University
The ability of soybean cyst nematode (SCN) populations to reproduce on germplasm lines used in soybean breeding programs was originally measured by a test called the SCN race test. Since 2002, an adaptation of the test, called the HG type test, has been in use.
Although 15 years have passed since the HG type test was introduced, confusion still exists about the concepts of SCN race and HG type. To help illustrate the concept of HG types, we drew a comparison between the current SCN HG type test and a hypothetical test for human food sensitivities that may provide a new perspective and make HG types more easily understood.
Thu, Apr 6, 2017
by Yuba Kantel and Daren Mueller, Soybean Plant Pathologists, Iowa State University
In our regional field tests we did not find that early planting (first week of May in most locations) increased the amount of SDS that developed later in the season compared to mid-May and later plantings, nor did we find a correlation between soil temperature at planting and SDS development. The soil temperature at the early planting dates had reached 55 to 60° F., the minimum germination temperature for soybean.