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Title:Stewarding chemical control in tall waterhemp (Amaranthus tuberculatus) while foregoing statistical significance
Author(s):Alexander, Brendan Craig Stewart
Director of Research:Davis, Adam S
Doctoral Committee Chair(s):Davis, Adam S
Doctoral Committee Member(s):Hager, Aaron G; Martin, Nicolas F; Tranel, Patrick J
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):integrated chemical management
waterhemp
herbicide resistance
population growth
statistical significance
biological relevance
Abstract:Tall waterhemp (Amaranthus tuberculatus) has become a considerable problem in U.S. agriculture, especially in corn and soy cropping systems. A particularly concerning characteristic of waterhemp is its ability to rapidly evolve resistance to herbicides. While chemical control is only one component of integrated weed management, it has proven to be extremely valuable and, therefore, we should prevent its loss. It is not reasonable to believe that applying more herbicides will stop the evolution of resistance to herbicides, but models and research suggest that applying tank mixes with multiple modes of action could potentially slow down the evolution of some types of herbicide resistance. Presupposing that tank mixing will slow the evolution of resistance to herbicides, we investigated possible tank mix partners for isoxaflutole and glufosinate and evaluated whether increasing the number of modes of action will maintain efficacy while allowing for reduced application rates. Next, we provide evidence that measuring the rate of evolution to herbicide with empirical field studies may require more resources than we originally thought due in part to (we believe) treatment contamination through pollen swamping resulting in small effect sizes that require at least an order of magnitude more progeny waterhemp seed for greenhouse studies. Then, we show that investing in more complex tank mixes for chemical weed control now may pay dividends in the future by resulting in lower cumulative costs or more robust overall control even though it may not be apparent in the first year. By “robust control” we mean that the more complex herbicide mixtures appear to be less sensitive to uncertainty in seed bank returns year to year, which is desirable since waterhemp has an extreme capacity for producing seed if given the opportunity. Finally, we do this all without using p-values, statistical significance, and null hypothesis tests (which is certainly an unorthodox strategy for scientific research projects).
Issue Date:2021-04-21
Type:Thesis
URI:http://hdl.handle.net/2142/110833
Rights Information:Copyright Brendan Alexander 2021
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05


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