Date Available

3-9-2020

Year of Publication

2020

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Plant and Soil Sciences

Advisor

Dr. Travis Legleiter

Abstract

Dicamba-resistant soybean along with lower volatility dicamba formulations have been introduced in an attempt to control herbicide resistant weeds such as Amaranthus palmeri. This introduction has increased the amount of dicamba being applied later in the growing season increasing the prevalence of dicamba off-target movement. Dicamba damage was simulated by applying low rates of dicamba directly on soybeans at rates (0.5 g ae ha-1, 1 g ae ha-1 and 5 g ae ha-1 dicamba) and five-exposure timings from June 1 to July 10. The experimental design was a randomized complete block with four replications at five locations. Crop and trifoliate injury ratings were taken 21 and 28 DAE (days after exposure) as well as yield, canopy closure ratings 21, 28 and 35 DAE and Palmer amaranth density was determined in both 2018 and 2019. When comparing injury across exposure dates it was observed that the early June exposures resulted in peak injury at 21 DAE whereas the late June and early July exposure peaked at 28 DAE. Yield was only reduced in 2019 with the lowest yield occurring due to exposure on June 20 at 5g ae ha-1. Differences were observed in canopy closure in both years, with a more pronounced and prolonged canopy closure delay in 2019. Overall dicamba exposure date had a greater influence on canopy development than exposure rate likely due to variations in soybean growth stages at the different exposure dates.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.058

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