By now, your soybeans should be in the ground — and hopefully on a good growth trajectory. But even though your crop might look fine from behind the windshield of your truck, it’s important to scout your fields and dig up some roots to ensure your soybean plants are healthy. Early-season diseases such as Pythium, Phytopthora and Rhizoctonia could be lurking at or beneath the soil, undermining your crop’s success at harvest.
Soybean seedling diseases usually cause plants to rot in the ground, grow poorly or die prematurely. Often, the roots themselves rot. On the stem at the soil line, on down to the root zone is where the action is. Typically, the worst-case scenarios involve cool, wet soils and compaction. If you didn’t plant under ideal seeding conditions (that is, relatively dry), you heighten the probability that one or more of these diseases are going to be a problem.
Here are the symptoms* to look for with each disease.
Pythium Seedling and Root Rot: Can attack and rot seeds preemergence. The characteristic indication is soft, brownish rotting tissue. In established plants, secondary roots can be soft and rotted; in some cases, plants may be stunted or die.
Phytopthora Seed and Seedling Blight: Can attack and rot seeds preemergence. At the V1 stage, infected stems appear bruised and are soft. Secondary roots are rotted, leaves turn yellow, and plants frequently wilt and die.
Rhizoctonia Root Rot: Damage prior to emergence is common, but hard to identify. Seedlings or older plants may be stunted and wilt. Plants might exhibit a firm, dry, brown to reddish-brown decay or a sunken lesion on the root and stem below or near the soil line.
What do to in-season
Scout your soybean fields now and dig up some roots. If you see evidence of seedling or root disease, plant seeds treated with a fungicide and insecticide next year. For example, Warden® CX seed treatment protects against Pythium, Phytophthora and Rhizoctonia, as well as Fusarium. It also inhibits a number of insects, such as aphids, leaf hoppers and thrips.
Use in-season imagery to discover areas that are not looking as healthy as other portions of the field. If you see evidence of one of these diseases, consult your agronomist to see if an application of an in-season fungicide and insecticide might help manage the problem.
Identify stress factors, such as saturation, by walking your fields and making sure your tile draining is working properly.
What to do next spring
Before planting, take a spade and dig down about 4 inches. Take a golf ball-sized amount of soil in your hand and squeeze it. If it’s crumbly but not loose, conditions are good for planting soybeans. If it remains in a ball, it’s probably too wet.
Plant treated soybean seed. This will give your soybeans disease and insect protection for approximately 21 days while you are spraying your corn, and until you can get back and spray your soybeans. This helps you manage your time and your risk.
Scout frequently during the season to monitor for insects and diseases.
* From the University of Illinois College of Agricultural, Consumer and Environmental Sciences website: http://cropdisease.cropsci.illinois.edu/soybeans. Accessed May 8, 2015.