Poster # 109

Luis Gehrke ¹, Connor Sible ¹ Mara Krone ¹, Santiago Mideros ¹, Jessica Rutkoski ¹
1. University of Illinois at Urbana-Champaign, Department of Crop Sciences, Urbana, Illinois

Gehrke, Luis

luiseg@illinois.edu

Growth regulators (GR)s are commonly applied to wheat in Illinois. While GRs may enhance yield in some environments, their impact on Fusarium head blight (FHB) has not been evaluated. Plant height is often negatively correlated with FHB symptom expression, with shorter varieties tending to manifest higher levels of disease. This may be because the wheat spikes of shorter plants are closer to the soil where they are more exposed to humidity and inoculum. We hypothesized that GRs could exacerbate FHB but improve yield by reducing plant height. To test this, we evaluated the effects of trinexapac-ethyl (active ingredient in Palisade® EC) and chlormequat chloride (active ingredient in Manipulator™) on FHB symptoms, yield, and height under intensive management. Two field trials were conducted during the 2025 season, one at Urbana and another at Belleville, IL. Each trial used a six-replicate split-plot design with chemical treatment as the main plot and variety as the subplot. Three commercial varieties with matching jointing and anthesis dates were tested under six treatment combinations: untreated control, Miravis® Ace applied at anthesis, and each GR with or without subsequent Miravis Ace application. Trials were not inoculated, though Belleville experienced high natural FHB infection. Data were collected for FHB severity (SEV), incidence (INC), Fusarium-damaged kernels (FDK), deoxynivalenol (DON), test weight, grain yield, and plant height. Lodging was not observed. Analysis of variance followed by Dunnett’s post hoc tests were used to assess treatment effects relative to controls. The main effect of GR was significant for SEV, DON, test weight, grain yield, and plant height. Only trinexapac-ethyl significantly affected these traits compared to the control. Surprisingly, trinexapac-ethyl reduced SEV by 5 percentage points across sites and by 9 percentage points at Belleville. When examined by variety, the effect of trinexapac-ethyl on SEV was greatest for the variety 'AgriMAXX 513'. Trinexapac-ethyl also reduced yield but increased test weight relative to the control. This study is ongoing with a second year of data collection in progress. Current findings suggest that GRs do not hinder FHB control, but they also may not improve yield in the absence of lodging. Trinexapac-ethyl may reduce SEV in some varieties through mechanisms that are not yet understood.

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