After taking much of the growing season off, soybean diseases are finally starting to wake up and make a bit of noise. Daren Mueller, an Iowa State University Extension plant pathologist, provides the following scouting tips and management information.
* Soybean rust: Yes, you read correctly, a soybean rust update. It has been a few years since we've talked about soybean rust. University of Illinois plant pathologist Carl Bradley has a nice article on the status and risk of soybean rust in Illinois. The article includes information on 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," says Mueller. "As of now, most of the soybean rust being found in fields is too far east in the southern United States for those fields to provide spores that could infect Iowa fields. But it is certainly worth keeping an eye on over the next several weeks because in Iowa we do have late-planted soybeans that could be affected."
For the latest distribution of soybean rust in the United States, visit the IPM PIPE webpage. If you suspect you have soybean rust in your field in Iowa, please send the soybean leaves to the ISU Plant and Insect Diagnostic Clinic at Ames.
* Sudden death syndrome: Sudden death syndrome, or SDS, has been reported in several counties in southeastern Iowa this summer. As a reminder, SDS typically shows up in patches, often at the edges of fields or in low-lying areas. See the photos accompanying this article to get a look at what the early and more advanced symptoms of SDS look like. Remember to split the stem open and differentiate SDS from brown stem rot. Brown stem rot is a disease which will have the characteristically brown discolored pith inside the stem. An SDS infestation doesn't turn the tissue brown inside the soybean stem.
With support from USDA and checkoff dollars, ISU plant pathologist 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," says Mueller. "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."
Her address is: Dr. Leonor Leandro, 351 Bessey Hall, ISU, Ames, IA 50011
Email: [email protected]
* Soybean vein necrosis virus: "We continue to see soybean vein necrosis virus, or SVNV, in Iowa," says Mueller, "especially the southern half of the state. However, most fields that have this virus in them have fairly low levels of the disease. See the previous ICM article for information on how to identify this disease."