After taking much of the growing season off, soybean diseases are finally starting to wake up and make a bit of noise.
Yes, you read correctly, a soybean rust update. It has been a few years. Dr. Carl Bradley has a nice article on the status and risk of soybean rust in Illinois. The article includes the most common look-alike diseases.
In general, soybean rust is building up in the southern states a bit sooner than previous years, and there are quite a bit of late-planted soybeans that could be affected in these southern states. As of now, most of the soybean rust finds are too far east for them to provide spores that could infect Iowa fields. But it is certainly worth keeping an eye on over the next several weeks because we do have late-planted soybeans that could be affected. For the latest distribution of soybean rust, visit the IPM PIPE webpage. If you suspect you have soybean rust, please send soybean leaves to the ISU Plant and Insect Diagnostic Clinic.
Sudden death syndrome
Sudden death syndrome (SDS) has been reported in several counties in southeastern Iowa. As a reminder, SDS typically shows up in patches, often at the edges of fields or in low-lying areas. See images for early and more advanced symptoms. Remember to split the stem to differentiate from brown stem rot, which will have the characteristically brown discolored pith.
With support from USDA and checkoff dollars, Dr. Leonor Leandro is collecting isolates of the fungus that causes SDS from across Iowa. If you have SDS in your field, we are very interested in collecting a few infected plants for research purposes. If you can mail a few infected plants, including the roots, to the address below or send an email to Dr. Leandro or myself to arrange for us to get the plants, it would be very much appreciated.
Soybean vein necrosis virus
We continue to see soybean vein necrosis virus (SVNV) in Iowa, especially the southern half of the state. However, most fields that have the virus have fairly low levels. See the previous ICM article for information on how to identify this disease.