For a refresher on how to sample for SCN, here is a link to sampling by one of our newly minted Ph.D. students (#8 in the series) https://plantpath.osu.edu/about-us/multimedia
2. Check your varieties – what are the disease resistant scores. Most farmers in Ohio know which fields have had diseases, Phytophthora root and stem rot, Sclerotinia stem rot, Frog eye leaf spot and replanting due to seedling diseases. All of these are best managed with resistance. Each company uses a different scoring system.
1 to 9 – where 9 is dead and 1 is little to no disease
1 to 9 - where 9 is best – top rating and 1 is tons of disease and plants are dead
As you look at these ratings you are going to see that most of the varieties are in the range of 3 to 7 – in the middle. This is because the resistance that we most commonly deploy takes many genes (quantitative) to manage the particular disease and under conditions that are highly favorable for disease development some disease will occur.
3. A good example is Sclerotinia stem rot – varieties with the highest resistant ratings will develop 6 to 15% incidence under high disease conditions, well below where overall yield loss can occur.
Do you have a seed treatment? Is it the right package for your conditions? Replanting is costly. From a seed, herbicide and delayed planting perspective. In Ohio, soybean seedling pathogens are very diverse and include the watermolds (Phytophthora and Pythium) as well as true fungi (Fusarium spp. and Rhizoctonia). All of these are very well managed with seed treatments, but there is not one fungicide that will control this plethora of pathogens. The mainstay, metalaxyl/mefenoxam is very good for P. sojae and some Pythium spp, the same is true for ethaboxam. A strobilurin will have efficacy towards some Pythium spp. and some true fungi. Fludioxonil and several other chemistries will manage Rhizoctonia and Fusarium,. The key for today’s seed treatment mix is to be sure you have several fungicides in the package,that will actually mix and work well together.