One of these weeks it will actually warm up and we will get to plant the 2011 crop! If you start getting anxious and want to put soybeans into cold soil, you may want to rethink this option. A very nice study was just published by Iowa State Researcher Leonor Leandro, which compared inoculations of soybean seed with the sudden death syndrome pathogen, Fusarium virguliforme. Seeds that were inoculated at the day of planting developed symptoms at all of the temperatures tested. Seedlings that were three and seven days old developed more root rot and greater severity of foliar symptoms at cooler temperatures (62° and 73° F) than those inoculated at warmer temperatures (82° F). Their conclusions were that soybean seeds are more vulnerable to infection than seedlings, but seedlings grown in cold soils are also vulnerable. For Ohio producers who must manage sudden death syndrome, this study indicates that it may be best to wait until the soils are warmer and plant at optimum conditions for seed germination.
Lots of products are going onto soybeans to provide protection from many soil-borne pathogens as well as insects. You can download a PDF from Ohio State that separates the insecticides from those that are fungicides as well as which soil borne pathogen they actually work against.
Replanting is one of the major reasons to consider using a seed treatmentfungicide. In addition to fields that have a history of poor stands, those that are in continuous soybeans and no-till may also benefit from a seed treatment. All of these conditions favor the build-up of inoculum for soil-borne pathogens. Replanting of both soybean and corn have become issues in Ohio over the past eight production seasons. Based on surveys from problem fields in the state over the past decade, the spectrum is quite diverse, and includes several water molds (Phytophthora and Pythium) as well as Fusarium graminearum (same fungus that causes head scab, corn ear and stalk rot), Rhizoctonia and charcoal rot. Seed treatments can be very effective for protecting seedlings when environmental conditions are very conducive to seedling infection. However, not all seed treatment products protect against all of the different seedling pathogens. Product active ingredients and rates of application are all key components for protecting seedlings when the correct environmental conditions occur for seedling diseases to develop.