Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
Figure 1: Low canopy Septoria brown spot (Photo: A. Koehler)
Full season soybeans across the area are approaching or at R3. Overall, the heat and dry conditions of the past few weeks have kept disease pressure low across the region. There have been a few reports of low canopy Septoria Brown Spot (Figure 1), particularly in irrigated fields. This disease usually stays to the bottom of the plant, limiting yield impact. Fungicide applications in soybean are most economical when disease is present and fungicides are applied during R1-R6 growth stages, with R3 being the most common timing. If you have disease present, and are considering a fungicide application, it is important to scout fields and monitor the weather. Most soybean diseases are favored by humid, wet conditions. If weather patterns continue to be hot and dry, disease pressure will likely remain low. However, we do often see wet falls, so continue to monitor rainfall and disease pressure through R6. The 2021 National Fungicide Efficacy Recommendations for Foliar Diseases of Soybean can be found at https://crop-protection-network.s3.amazonaws.com/publications/fungicide-efficacy-for-control-of-soybean-foliar-diseases-filename-2021-03-12-182833.pdf. I have also included results from the 2020 irrigated full season soybean foliar fungicide efficacy trial conducted at the Carvel Research and Education Center. Disease pressure was low in 2020 and there were no ratable levels of foliar pathogens present.
2020 Soybean Foliar Fungicide Trial
2020 Soybean Foliar Fungicide Trial