By Darren Hefty

2016 was quite a year!  Unfortunately for some it was an especially damaging year to their soybean crop from soilborne diseases.  Don’t think you had any?  Hopefully you didn’t, but here are some signs to look for that may be an indication that diseases are a problem in your soils.

  1. Emergence issues – If your crop is slow to come up or your stand is uneven, odds are a disease or an insect is striking your seed or root system.  Here is where many call their seed company to complain about poor germination when the real answer can be determined by digging up some seeds.
  2. Inconsistent health, plant to plant – If plants in patches or even just one plant here or there looks a little sickly, digging up plants and even splitting a few open will often reveal the early signs of disease.
  3. Dead plants – With some plant diseases, plants may emerge, but they die and senesce quickly.

With all of these signs/symptoms and more, there are multiple diseases and other problems that could be present in the field.  If you are unable to diagnose the plants, you have a couple options.  Either you can send in samples to a university or a lab or you could download a free app.  We worked in conjunction with the American Phytopathological Society to put together the Ag PhD Soybean Disease App.  Download your free copy today for your smartphone or tablet. Available on iOS and Android.

Here are some common issues we are seeing in fields across the country.

Phytophthora Root and Stem Rot – This pathogen is so tough because it can affect soybeans from planting to maturity and every stage in between.  Seed treatment usage is very good for helping with the early stages of phytophthora, but a resistance gene effective on the strain of phytophthora present in your field is needed for season-long protection.  Look for patchy areas within a field often in poorly drained or slowly drained and heavier soils.  There is often a chocolatey-brown coloration that comes up the outside of the stems from the ground, as well as a damping off look to the plants.  Continuous soybeans can lead to a higher incidence of phytophthora.

Pythium Blight and Root Rot – Pythium is often referred to as damping off and can happen to the seed below the ground or the entire plant after emergence.  It most commonly occurs in saturated soils and poorly drained ground.  Some strains of pythium like cooler soils, especially around early planting, while others like warmer soils later in the season.  Metalaxyl (and other close relatives) has been the standard seed treatment for pythium protection.  The new active ingredient ethaboxam, found in Intego, adds an additional chemistry to fight this disease and has performed well in fields across the country.

Rhizoctonia Blight and Root Rot – Just when you thought there was a pattern with poorly drained soils being the problem, along comes rhizoctonia.  It’s most common in light, sandy soils and the fungicides that stop it are not the same ones used for pythium control.  The most frequently observed symptom that is noticed in soybean fields with rhizoctonia infections is reddish, sunken lesions on the hypocotyl.  If that’s not enough to kill the plant, it may linger and take the plant down at a later stage.  The key, besides a good seed treatment package with multiple fungicides, is to reduce all other stresses in the field.

Sure, there are many other diseases we could discuss.  Just remember to lock in the best seed treatment package to stop these very common diseases.  For images and more information on the above diseases as well as many others, download the free Ag PhD Soybean Diseases App to help you identify any problems that do show up in your field this year.