Announcement of Final Thesis Defense Crop and Soil Science M.S. Degree: Candidate’s Name: Kaddi Gewirtz
August 14, 2026 2:00PM - 3:00PM
Plant and Soil Sciences Building Room A271
Candidate’s Name: Kaddi Gewirtz
DEVELOPING FALL WEED MANAGEMENT STRATEGIES IN WINTER WHEAT AND ASSESSING MESOTRIONE CARRYOVER RISKS IN EARLY-PLANTED SOYBEAN
Members of the Examining Committee and their Department:
- Dr. Christy Sprague, Plant, Soil and Microbial Sciences
- Dr. Maninder Singh, Plant, Soil and Microbial Sciences
- Dr. Christina DiFonzo, Department of Entomology
ABSTRACT
Variable Michigan weather conditions have raised questions about the effectiveness of fall herbicide applications in winter wheat and the potential risk of increased mesotrione carryover from applications in the previous corn crop to early planted soybean. Field experiments were conducted across five site-years to evaluate weed control, crop tolerance, and grain yield following fall and spring herbicide applications in ideal- and late-planted winter wheat. Transient fall crop injury (9-18%) occurred only following mesosulfuron- and pyroxsulam-containing treatments and was limited to a few site-years. Regardless of herbicide treatment, weed suppression was consistent across all application timings and environments. These herbicide treatments suppressed weeds 90-98% and 77-98% in ideal- and late-planted wheat compared with the untreated control. Planting date, rather than herbicide treatment, was the primary factor affecting grain yield. Timely fall herbicide applications in ideal-planted wheat provide effective weed control and represent a reliable alternative when spring applications may be delayed. Field and greenhouse experiments were conducted to evaluate mesotrione carryover risk in rotational soybean and determine if metribuzin PRE in soybean increased crop injury. Although mesotrione is a widely used corn herbicide, concerns remain about its potential carryover effects on rotational soybean under certain environmental conditions. Greenhouse studies showed rate-dependent injury from both herbicides, with synergistic responses at high rates. However, in the field, injury occurred only at one low-pH (pH 5.9) site and declined substantially by 56 d after emergence. Planting date had a greater influence on soybean yield than herbicide carryover, with early-planted soybean consistently producing the highest yields. Under the Michigan soil and weather conditions examined, mesotrione carryover poses minimal agronomic risk to soybean yield when label restrictions and soil specific considerations are followed.
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