Nathan Kleczewski, Extension Specialist – Plant Pathology; email@example.com
Overall there have not been many new reports of diseases in field crops. We did see Northern Corn Leaf Blight (NCLB) this week. NCLB is residue borne and likes wet conditions and moderate temperatures. Unlike Grey leaf spot, NCLB forms large cigar shaped lesions that are often brownish/grey in color (Figure 1). A fungicide application between VT and R1, particularly if you are in an irrigated setting, might a good idea if you see NCLB on the 3rd leaf below the ear leaf or above.
Figure 1. A characteristic cigar shaped lesion caused by the Northern Corn Leaf Blight pathogen.
We have seen some cases of Fusarium blight in double crop soybean seedlings. Often this will pop up in poorly drained areas of the field or compacted soil. Other factors that can cause a flare up in Fusarium blight include herbicide injury, poor quality seed, insect or mechanical injury, and poor fertility. Infection often occurs when soils are saturated and symptoms may increase during droughty periods. Seedlings often die soon after emergence and roots and stems have a slightly brown/red appearance. The taproot is often rotted to some degree, and a proliferation of roots can sometimes be observed above the infected area. Minimizing compaction and stress and the use of a fungicide seed treatment may help in future years if planting into problematic fields.