Dean Reynolds, Extension Plant Pathologist
The "dreaded" root rots
How did the Soybean Cyst Nematode fair with all the Water?
Just fine thank you. Nematodes are aquatic animals so if you hoped that the rainy conditions and saturated soils were killing them think again. The nematode absorbs oxygen through its cuticles. As long as the water is aerobic, that is contains oxygen, the nematode will do fine. The SCN lifecycle, from egg hatching to females producing new eggs, typically takes four weeks to complete. However, because of the cooler conditions this spring the time period may be longer. If your plan on scouting your soybean fields for SCN by digging roots to find the females on the roots in suspect areas in fields, wait a little longer. Females will probably need at least another week to develop on the roots. If you wait, females will be more abundant and easily to see. Also, since soybean growth has been slow, root growth will be limited for nematodes to infect and females to develop. Waiting a few more weeks would be best. After all there is nothing you can do this year to manage them in the current soybean crop. Management planning can be done this fall.
Bacterial Spots on Soybeans
Bacterial leaf spots have been appearing on unifoliate or trifoliate leaves of soybeans because of the constant wet conditions and high relative humidity. The bacteria actually live on the surface of the soybean leaf and take advantage of the cool temperatures and moisture. These early bacterial infections will probably not persist and will not cause economic problems. Hot dry weather will check bacterial growth. Typically, bacterial leaf spots are seen later in the season on soybean plants approaching maturity. Pictures and further discussion of soybean diseases can be found at our web site http://www.extension.umn.edu/agriculture/crop-diseases/soybean/.
Corn seedlings had been coming into the plant disease clinic with rotted mesocotyls caused by either Pythium and/or Fusarium root rots. We are now probably past that concern.