By Diane Plewa
Every year, the University of Illinois Plant Clinic cooperates with the Illinois Crop Improvement Association and the Illinois Department of Agriculture to certify crops for export purposes. We certify mostly corn and soybean fields, with the occasional sorghum and sunflower samples to liven things up.
We started receiving corn samples a few weeks ago. So far, we've seen a large number of foliar fungal diseases including Gray Leaf Spot (upper left in picture) and Northern Corn Leaf Blight (lower left in picture). Minor diseases (such as anthracnose, Phyllosticta yellow leaf blight, and Physoderma brown spot) are also showing up frequently, probably due to the favorable weather we've had for fungal pathogens. Common and southern rust are also showing up with regularity. So far this season we have not diagnosed any samples with Goss's or Stewart's bacterial wilt in corn, which is not terribly surprising given the weather conditions we've had this growing season.
Soybean fields are usually sampled after the corn fields so we haven't received any phytosanitary certificate samples in soybeans yet, but in samples submitted by farmers we've seen a number of common fungal diseases including Sudden Death Syndrome (right picture), Brown Stem Rot, and Septoria brown spot. We have also seen a few samples with Pod and Stem blight. A major complaint this season has been stunting in soybeans. We've found that, in the majority of the samples submitted to the Plant Clinic, this is due to a root issue. The cool, wet weather we saw across the state at the beginning of the season was perfect for a number of common root rot pathogens, including Phtophthora, Pythium, and Rhizoctonia. However, even in plants where we did not see any evidence of a root pathogen, many root systems were not well-developed early in the season leading to poor establishment and stunting.