By Dusty Sonnenberg, CCA, Ohio Field Leader, a project of the Ohio Soybean Council and Soybean Check-off
As farmers scout their fields, it’s important to be alert and correctly identify the symptoms of soybean diseases. While there are many common foliar diseases that affect Ohio’s soybean fields, there are some new diseases that have not yet been discovered in Ohio but have been in surrounding states.
“With the rain and moisture that some parts of the state have at this time of the growing season, it makes sense to take a surveillance approach. Last year, we heard reports of other soybean diseases in other neighboring states, but they have not yet appeared in Ohio,” said Dr. Horacio Lopez-Nicora, a soybean pathologist and nematologist at OSU. “Red crown rot is a disease whose foliar symptoms are very similar to SDS. It attacks the root system of a plant and significantly impacts yields. To us, it is a new pathogen that is easily overlooked and dismissed as just a bit of SDS and not the beginning of red crown rot. The difference between SDS and red crown rot is that there is a very red discoloration at the bottom of the stem and the fruiting body that the fungus produces is very red and is located at the bottom of the lower parts of the stem of infected plants.”
“Now is the time when we may see frog eye leaf spot or Septoria brown spot, but we may also see another leaf spot disease that is not the same as frog eye leaf spot or Septoria brown spot,” Lopez-Nicora said. “Targe spot is another new disease that is emerging in the southern states. It looks very similar to frog eye leaf spot and Septoria, but it is not exactly the same. It can occur, and growers need to be vigilant in observing if they spot a leaf disease.”
Another nematode to watch out for is the root-knot nematode. “The root-knot nematode is another nematode that damages a plant’s root system and produces galls,” Lopez-Nicora said. “The roots appear enlarged compared to normal and the galls interfere with nutrient and water uptake. Symptoms include stunted plants and, on very hot days, wilting.”
Red crown rot is a soil-borne pathogen. The movement of soil from field to field on agricultural equipment allows this pest to spread easily. Root-knot nematodes also spread most easily through the movement of soil. Tillage and planting equipment can transport soil from an infected field. Target spot is a fungal pathogen that produces spores that are airborne and can move from one state to another on weather fronts.
