By Dr. Horacio Lopez-Nicora, OSU Extension soybean pathologist and nematologist, adapted from CORN 2024-26
During our field survey this past week, it became apparent that soybean vein necrosis virus (SVNV) is significantly present in our soybean crops in various regions. SVNV, a viral disease transmitted primarily by thrips, typically manifests as yellowing and necrosis along the veins of soybeans’ leaves. Initial symptoms include chlorotic lesions that develop and produce a necrotic, vein-associated appearance. The impact of SVNV on overall yield is still being studied, but early infection is generally more damaging. Growers should be alert to thrips populations and use integrated pest management strategies, including the use of resistant varieties when available, to help control the spread of this virus.
In parallel with the increase in SVNV cases, we have also seen an increase in downy mildew infections. Downy mildew, caused by the oomycete Peronospora manshurica, appears on the upper surface of leaves as pale green to yellow spots that spread and can eventually cause leaves to curl and become necrotic. On the underside of leaves, the pathogen produces a grayish, fluffy growth. This pathogen thrives in cool, moist conditions, making our recent weather patterns conducive to its spread. The disease rarely causes severe damage to a crop, but there are some reports that it reduces seed size and quality when it occurs early in the season and in large quantities. Effective control includes crop rotation, planting clean seeds, and resistant varieties. Fungicides commonly used on soybeans are not recommended for downy mildew.
Observation is critical to detect an outbreak early and take timely countermeasures. By carefully monitoring crops and implementing proactive management practices, we can effectively control these diseases and protect our soybean yields. Walk your fields, look for soybean diseases, and send your samples to the Ohio State University Soybean Pathology and Nematology Laboratory.
For more information on submitting a sample to our laboratory, click HERE.
Send your samples to:
OSU Soybean Pathology and Nematology Laboratory
Attn: Horacio Lopez-Nicora, Ph.D.
110 Kottman Hall
2021 Coffey Rd.
Columbus, Ohio 43210
[email protected]
