EFFICACY AND ECONOMICS OF CULTURAL AND MECHANICAL WEED CONTROL PRACTICES FOR HERBICIDE RESISTANT WEED MANAGEMENT.

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1000664
• Grant No.: 2014-67013-21551
• Cumulative Award Amt.: $500,000.00
• Proposal No.: 2013-02325
• Project Start Date: Jan 1, 2014
• Project End Date: Dec 31, 2018
• Grant Year: 2014
• Program Code: [A1131]- Plant Health and Production and Plant Products: Controlling Weedy and Invasive Plants

Recipient Organization
UNIVERSITY OF WYOMING
1000 E UNIVERSITY AVE DEPARTMENT 3434
LARAMIE,WY 82071-2000

Performing Department
Department of Plant Sciences

Non Technical Summary
Cultural and mechanical weed management practices are underused in many cropping systems, particularly for herbicide-resistant weed management. This may be due, in part, to a lack of knowledge of the impact of non-herbicide management practices on herbicide-resistant weed development. Modeling is currently the most common approach for comparing the impact of weed control practices on herbicide-resistant weed evolution. Nearly all modelers recognize the importance of validating assumptions and results of predictive models through field research, yet there is an alarming lack of field studies that quantify the impact of non-herbicide weed management practices on the evolution of herbicide-resistant weed populations. We propose conducting field studies to quantify the impact of tillage and diverse crop rotations on the development of herbicide resistance in a summer annual weed species with relatively short soil life. We will establish a kochia (Kochia scoparia) population throughout our study site with a known proportion of ALS-herbicide susceptible (S) and resistant (R) individuals, and monitor the proportion of R:S as well as total weed density in response to tillage intensity, crop rotation, and herbicide use. Based on the results of this study, we will develop biological and economic models that will aid in developing herbicide-resistant weed management recommendations that go beyond herbicide use patterns. By determining the efficacy and economic impacts of non-herbicide practices on development of herbicide resistance, we hope to decrease the reliance on herbicides, thereby reducing the evolution and spread of new herbicide-resistant weed biotypes.

Animal Health Component

90%

Research Effort Categories

Basic

5%

Applied

90%

Developmental

5%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
213	2300	1140	100%

Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
2300 - Weeds;

Field Of Science
1140 - Weed science;

Keywords

herbicide resistance

weed management

Goals / Objectives
Our long-term goal is to understand the impact of non-herbicidal weed control practices on development of herbicide-resistant weed populations in order to develop sustainable cropping systems that prolong the utility of existing herbicide resources. In order to accomplish our long-term goal, we propose the following specific objectives for this research project: 1. Determine the impact of crop rotation diversity and tillage on enrichment of an herbicide resistance trait within a weed population. 2. Quantify the economic benefits and risks of adopting a diversified weed management program to delay the development of herbicide resistance. 3. Evaluate the fitness of the most common mutation that confers resistance to acetolactate-synthase (ALS)-inhibiting herbicides in Kochia scoparia (Trp574) under field conditions.

Project Methods
An experimental kochia population will be developed with a known resistant (R) to susceptible (S) ratio. The experimental kochia population will be seeded at all field study locations (3) prior to initiation of the field studies. Three field sites will be established under sprinkler irrigation at Research and Extension Centers near Powell, WY, Scottsbluff, NE, and Huntley, MT. Sites will be chosen in areas without major kochia infestations, so that the experimental kochia population that is seeded will be the primary source of kochia seed. A series of tillage, crop-rotation, and herbicide treatments will be imposed at all field sites. Soil sampling will be conducted each fall to determine the impact of tillage, crop rotation, and herbicide treatments on total kochia density and R:S ratio. A mixed-model ANOVA will be used, considering site and block within site random effects. Tillage, crop rotation, herbicide treatment, and all interactions among these three factors will be considered fixed effects. Response variables will include kochia control, seed production, and kochia seedling density (field measurements), kochia seed density (exhaustive germination), proportion of R seed in the seed bank (greenhouse screening), and total R seed density (proportion of R seed multiplied by seed density). The R:S ratio in the absence of ALS-inhibiting herbicides at the end of the study will provide insight into whether a major fitness cost is associated with the Trp574 mutation in kochia. The mixed-model analysis will allow us to determine the relative benefit (if any) from tillage and crop rotation for each of three herbicide use patterns. The probability of resistance evolution at distinct time points will then be modeled for each crop rotation, tillage system, and herbicide combination using the change in R:S ratio and total seed density. A model similar to that proposed by Neve et al. (2011a; 2011b) will be used to calculate the resistance risk from each tillage and crop rotation combination in the presence and absence of herbicide selection pressure. Biological model parameters such as germination proportion, natural mortality, and loss of seed viability may be influenced by tillage and crop rotation, and thus may impact the risk of resistance. We will use data from our studies to inform selection of these parameters. A linear programming model similar to Lee (2012) will be used to assess the economic impact of tillage and crop rotation at the farm-level for each herbicide use pattern. A Monte Carlo process will be used to select input costs associated with different tillage and crop rotations (such as fuel prices, labor costs, fertilizer prices, etc.) and crop prices (corn, wheat, dry bean, and sugar prices) based on historical data. The Monte Carlo process randomly draws inputs over numerous iterations (10,000 in our case) and the linear programming model determines optimal decisions over each set of random draws. The stochastic nature of the Monte Carlo process (variables of interest being randomly drawn from known distributions) allows for great sensitivity analysis and risk analysis based on a wide range of feasible prices and physical relationships. The objective of the linear programming model will be to determine the optimal crop rotation and tillage regime under various herbicide use patterns (complete reliance on ALS-inhibiting herbicides, tank mixtures, and complete avoidance of ALS-inhibitors). This approach will allow us to incorporate the risk of herbicide-resistant weed development estimated in the previous model into an economic model. Changing herbicide use patterns is a relatively simple cost calculation for growers; whereas incorporating tillage and additional crops is much more complex, and will require greater planning and management. It is important to determine the benefit of adopting these practices with respect to resistance risk, and also the economic benefits and risks. This approach will allow us to do both.

Progress 01/01/14 to 12/31/18

Outputs
Target Audience:Reports were provided to scientists working in pest management and agronomy, extension stakeholders responsible for managing crop and pest management activities, pesticide applicators and farmers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two graduate students have included components of this project as their primary dissertation work, and one will have at least three dissertation chapters primarily based on this research. How have the results been disseminated to communities of interest?Presentations have been given at scientific societymeetings (Weed Science Society of America, Western Society of Weed Science) as well as campus seminars at Nebraska and Wyoming, and many extension field days. One peer-reviewed publication is under review and three more are in preparation. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? 1. All main effects (tillage, crop rotation, and herbicide) affected kochia density (P<0.001), but only herbicide treatment had a marginal effect on R:S ratio (P=0.078). Use of ALS-inhibitor mixtures resulted in the lowest R:S as well as the lowest density of resistant kochia (16 plants per m-2) compared to the annual ALS rotation or complete reliance on ALS herbicides (113 and 144 plants per m-2, respectively). Annual intensive tillage reduced resistant kochia density to 50 plants per m-2 from 81 plants per m-2 observed in minimum tillage. The most diverse (four crop rotation) and least diverse (continuous corn) crop rotations resulted in the lowest resistant kochia density (39 and 45 plants per m-2) followed by the three- and two-crop rotation (79 and 117 plants per m-2). 2. Costs associated with implementation of each treatment were summed, and compared to historic data from each region. An enterprise analysis was used to analyze data, and results were reported in a partial budget format. Crops treated with a herbicide mixture including ALS inhibitors that were annually intensively tilled consistently had higher economic returns than all other treatment combinations. Lowest crop returns were typically observed in ALS inhibitor herbicide treatments that were minimally tilled.

Publications

• Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Mosqueda et al. (2019) Effect of Crop Canopy and Herbicide Application on Kochia (Bassia scoparia) Density and Seed Production. In Review.
• Type: Conference Papers and Presentations Status: Accepted Year Published: 2019 Citation: Mosqueda et al. (2019) Economics of Cultural, Mechanical, and Chemical Weed Control Practices for Herbicide-Resistant Weed Management. Proc. Western Soc. Weed Sci

Progress 01/01/17 to 12/31/17

Outputs
Target Audience:Extension tours were given at 4 research sites in Wyoming, Nebraska, and Montana, reaching crop consultants, farmers, agronomists and other scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Multiple graduate and undergraduate students at 3 universities have been involved in the research, allowing them to learn field ecology and agronomy research practices. How have the results been disseminated to communities of interest?Extension field days, scientific conference presentations, and professional workshops were conducted. What do you plan to do during the next reporting period to accomplish the goals?We will be finalizing the data collection and analysis, and summarizing data for distribution through multiple channels.

Impacts
What was accomplished under these goals? The final year of the field study was finished in 2017, final data is being analyzed. It appears that both crop rotation and tillage mtigates the evolution of herbicide resistant weeds even under poor herbicide management practices.

Publications

• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2017 Citation: Mosqueda et al. (2017) Effect of Crop Rotation Diversity on Long-Term Kochia (Kochia scoparia) Management. Proc. Western Soc. Weed Sci. 49.
• Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2017 Citation: Mosqueda et al. (2017) Effect of Crop Canopy on Kochia (Kochia scoparia) Seed Production. Proc. Western Soc. Weed Sci. 59.

Progress 01/01/16 to 12/31/16

Outputs
Target Audience:An extension workshop was held in Scottsbluff, Nebraska that reached crop consultants, agronomists, and herbicide retail personnel. The study was also shown at various field days that reached a broad audience of community members, farmers, and ag professionials. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Workshops were held using the field study and data as integral components of the training materials, reaching 20 crop professionals that influence herbicide recommendations over many acres in the region. We have also trained several graduate and undergraduate students in the skills of field research and crop production. How have the results been disseminated to communities of interest?An extension workshop was held in Scottsbluff, Nebraska that reached crop consultants, agronomists, and herbicide retail personnel. Several presentations were made at society meetings that reached scientists and weed management professionals. What do you plan to do during the next reporting period to accomplish the goals?We are planning a summer field tour and workshops to disseminate current results to farmers and others who influence herbicide and cropping decisions in the regions.

Impacts
What was accomplished under these goals? Objective 1: We completed the third year of a 4 year rotation in 2016. Results to date suggest that increasing crop rotation diversity and tillage can mask many of the weed management problems associated with non-diverse herbicide programs. However, the lowest resistant kochia density was observed, as expected, in the treatments where crop diversity was combined with herbicide diversity in the form of mixtures. We will continue to collect data through the final year of the field rotation.

Publications

Progress 01/01/15 to 12/31/15

Outputs
Target Audience:Initial data are still being collected, and therefore no public outreach has been done except for field tours. Attendees at field tours include students, seed and chemical industry representatives, general public, and other agriculture scientists and extension agents. Changes/Problems:Due to planting difficulty, the small grains component of the rotation is winter wheat at 1 site, spring wheat at 2 sites, and barley at 1 site. All of these crops serve the same purpose with respect to crop and herbicide diversity, so the slight modification should not have a significant effect on the results. What opportunities for training and professional development has the project provided?Several graduate students have been involved in the project at all 4 sites. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Continue with the study as planned.

Impacts
What was accomplished under these goals? We successfully completed the second year of data collection. As the crop rotations are 4-years in length, data will be of limited use until the full rotation is completed. We maintained the integrity of the long-term treatments at all four study locations, and kochia density, seed production, and seed bank data were collected from all sites.

Publications

Progress 01/01/14 to 12/31/14

Outputs
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Four graduate students and one undergraduate student were heavily involved with the establishment and maintenance of the study. Training in general agronomic and weed science reserach methods was provided to all students involved. How have the results been disseminated to communities of interest? There are currently no results to disseminate. What do you plan to do during the next reporting period to accomplish the goals? We will continue collecting data on the long-term study as planned.

Impacts
What was accomplished under these goals? 2014 was the first year of a long-term project, and therefore we have made limited progress in meeting the specific objectives. The study was successfully established at 4 research sites in Nebraska (1), Wyoming (2), and Montana (1). Samples were collected from all sites, and soil and seed samples are currently being processed in the greenhouse according to schedule. Results from the first year will be analyzed and available by late summer of 2015.

Publications