Investigating herbicide and cover crop interaction in weeds

Paudel, Rama

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https://hdl.handle.net/2142/117564 Copy

Description

Title

Investigating herbicide and cover crop interaction in weeds

Author(s)

Paudel, Rama

Issue Date

2022-11-30

Director of Research (if dissertation) or Advisor (if thesis)

Davis, Adam S.

Doctoral Committee Chair(s)

• Davis, Adam S.
• Riechers, Dean E.

Committee Member(s)

• Hager, Aaron G.
• Williams II, Martin M.

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• S-metolachlor
• Cover Crops
• Allelochemicals
• Herbicide Metabolism
• Integrated Weed Management

Language

eng

Abstract

Cover crops are a useful component of integrated weed management (IWM). Cereal rye is increasingly used as a cover crop to manage herbicide-resistant weeds in soybean but is inadequate for complete weed control. S-metolachlor is a chloroacetamide herbicide widely used for residual control of annual grasses and small-seeded broadleaves. However, limited information is available to define mechanisms driving potential interactions between S-metolachlor and a cereal rye cover crop. Exploring these possible interactions may provide a novel opportunity to improve the weed control spectrum by combining a cereal rye cover crop and S-metolachlor. Potential mechanisms affecting interactions between cover crops and herbicides include physical and chemical mechanisms. The physical suppression of weeds through cover crops has been documented, but the role of cover crop allelochemicals independent of physical suppression and their interaction with S-metolachlor remains unknown. Weeds such as Abutilon theophrasti can detoxify S-metolachlor through glutathione-mediated metabolism. However, weed responses to the combined effects of multiple stressors, such as allelochemicals and S-metolachlor, may influence detoxification efficiency of weeds. My dissertation focuses on S-metolachlor and cereal rye cover crop interactions and underlying mechanisms driving these interactions. The first chapter of this dissertation includes a literature review describing current issues in weed management, integrated weed management, integration of cultural and chemical tactics in weed management, cover cropping, chloroacetamide herbicides, understanding mechanism of herbicide-cover crop interaction, herbicide and allelochemical metabolism in weeds and a review of broadleaf (Abutilon theophrasti) and grass (Sorghum bicolor) weeds used in my experiments and the concept of dose-response experiments in herbicide cover crop studies. In chapter two, I investigated the interaction between cereal rye cover crop and S-metolachlor on S. bicolor and A. theophrasti with S-metolachlor dose-response experiments in vermiculite medium using greenhouse-grown cereal rye. Results from soilless medium indicated that the cereal rye cover crop with a low dose of S-metolachlor is helpful in controlling weed species with natural tolerance to S-metolachlor, such as S. bicolor and A. theophrasti. Results from the soilless medium may not be applicable to field conditions since edaphic factors might affect an interaction. Therefore, in chapter three, controlled-environment dose-response experiments were conducted utilizing field-grown cereal rye and field soil with cereal rye root residues. However, cereal rye-amended field soil did not change the extent of control of A. theophrasti and S. bicolor. Weed species exposed to multiple stressors, such as cover crop allelochemicals from field soil and decomposing cover crop residues, may develop adaptation and detoxification mechanisms. Therefore, in chapter four, I investigated putative allelochemicals impacts on the ability of S.bicolor seedlings to metabolize S-metolachlor in laboratory experiments using the synthetic allelochemical, Benzoxazolin-2(3H)-one (BOA; obtained commercially), different densities of greenhouse-grown cereal rye (as a source of allelochemicals), and radiolabeled S-metolachlor. Cereal rye did not affect S-metolachlor metabolism in S.bicolor. Finally, chapter five summarizes my overall conclusions and suggests future research directions. I hypothesized that complementary stresses of cereal rye cover crop and S-metolachlor would interact synergistically to control S. bicolor and A. theophrasti. However, my experiments did not provide evidence to support a synergistic interaction.

Graduation Semester

2022-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/117564

Copyright and License Information

Copyright 2022 Rama Paudel

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