Improving our ability to manage sorghum stalk rot through fungicide and cropping system practices in Kansas

Abstract

Sorghum stalk rot is a worldwide threat to sorghum production and can severely compromise stalk integrity, leading to lodging and yield losses. Unfortunately, there are currently no in-season management options for stalk rots; management recommendations are limited to pre-planting strategies, such as hybrid selection and avoiding excessive planting densities. The first experiment evaluated the efficacy of fungicide application timing (at planting or flowering) and spray technology (at-planting banded dribbled 5.08 cm off-center below the row (2x2), a dribbled over the row (0x0), or a dribbled 5.08 cm off the row (0x2) placement, and foliar application at the beginning of flowering) for control of stalk rot diseases through on-farm trials. Research trials were established in three farmer fields located in Russell, Dighton, and Bavaria, Kansas during the 2023 and 2024 seasons. Fungicide applications had no significant effect on protein content, panicle size, disease severity, or disease incidence. Both the hybrid and the fungicide application significantly affected grain yield. Overall, applying Xyway™ LFR® at planting by dribbling over the row, and using Topguard® EQ and Adastrio™ at the start of flowering, increased yield compared to the control. Yields were higher with the 0x2 application, where fungicide was dribbled over the row, than with the 0x0 application. Foliar application of fungicide at flowering resulted in a greater yield increase than either planting application alone or combined planting and foliar application. These findings indicate that foliar applications at the flowering stage are the most consistent for maximizing sorghum yield. However, fungicide use did not significantly reduce stalk rot disease in this study. The second experiment evaluated the influence of different plant densities on sorghum grain yield components, stalk rot severity, and lodging under narrow (38.1 cm) and wide (76.2 cm) row spacing. The plant density observed in this experiment ranged from 59,000 to 160,000 plants ha⁻¹. Research trials were established in three farmer fields in Russell, Dighton, and Bavaria, Kansas, during the 2024 and 2025 seasons. Sorghum grain yield was consistently higher with wider row spacing across all the locations. Higher yields were observed in Bavaria, followed by Russell and Dighton. Additionally, a positive linear relationship between final stand and sorghum yield was observed. In 2025, stalk rot severity was significantly lower than in 2024. The probability of observing no stalk rot symptoms increased with higher plant density and lower drought stress during flowering, while severity was reduced by higher densities and lower stress during grain filling. Although lodging was observed only in one environment, limiting the assessment of yearly variation, stalk rot severity and wind speed were identified as the primary drivers of occurrence. In cases where lodging occurred, higher plant densities and wider row spacing significantly reduced lodging severity, whereas higher stalk rot severity directly increased the proportion of lodged plants.