Progress 07/01/05 to 06/30/08
Outputs
OUTPUTS: We have collected close to 500 horseweed seed samples (out of over 1300 sites visited) in Indiana. This sampling for detection of a herbicide-resistant weed is the most extensive ever conducted in the United States. This unique data set will allow us examine the effects of farming practices on the development and spread of herbicide resistance at a landscape level. We have shown that glyphosate resistant horseweed is present in 29 counties in Indiana. Its prevalence is mostly associated with no-till cropping systems and in fields with wheat or soybean as the previous crop. Resistance ratios of 2 to 44 have been found in selected populations. Cross resistance to glyphosate and ALS inhibitors has been found in about 8 to 15% of the populations. We have identified two populations with elevated tolerance to 2,4-D and will conduct more studies on the heritability of this trait. Field studies on the biology and management of this weed have shown that it is relatively easy to control simply by using something other than glyphosate for its control. Seedbank studies have shown horseweed seed is not persistent in the soil and that a resistant population can be exhausted within two years. We have found glyphosate-resistant giant ragweed in 14 counties and the resistance ratios of these populations range from 2 to 7. We have found common lambsquarter populations that show resistance ratios of 2 to 4. Additional studies on the fitness characteristics of these biotypes has shown that they grow more rapidly in the early part of the growing season and begin reproductive growth earlier than sensitive populations. PARTICIPANTS: Primary Research Collaborators - Kevin Gibson and Steve Weller - fellow faculty members at Purdue University. Mark Loux - faculty member at Ohio State University. Vince Davis, Andy Westhoven, and Greg Kruger - graduate students in my program who were responsible for much of the research. Andy completed a MS degree and is employed by AgriGold. Vince completed a Ph.D. and is a faculty member at the University of Illinios. Greg is working on a Ph.D. in my lab and should graduate in a year. We also collaborated with extension weed scientists at each institution in the NC Region on the development of the GWC publications (Glyphosate, Weeds, and Crops) and the GWC website (glyphosateweedscrops.org). We have distributed over 300,000 copies of these publications across the region. The publications were authored by various individuals and reviewed by the entire group of weed scientists. We also collaborated closely with the Indiana Soybean Alliance, the Illinois Soybean Board, and a number of life sciences companies and received some supplementary funding for this work. TARGET AUDIENCES: The target audience was soybean and corn growers in the eastern cornbelt, and the crop protection industries that serve these growers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Dr. Johnson's lab developed a website which provides details of his research on the biology, distribution and management of glyphosate-resistant horseweed in Indiana (Welcome to the Home of Horseweed http://www.btny.purdue.edu/weedscience/marestail/index.htm). This website was the first site in the U.S.A. devoted to dissemination of information on a glyphosate-resistant weed in U.S. row crop systems. In addition, he led the development of a publication with colleagues at the University of Illinois and Ohio State University titled "Horseweed Biology and Management (ID323/GWC9)", which was co-funded by the Indiana Soybean Board, the Illinois Soybean Program Operating Board and Ohio State University. Dr. Johnson and his colleagues have distributed over 31,500 copies of this publication. In addition, he was invited to an international herbicide resistance symposium (Rothamsted Resistance) in the U.K. to present his research on glyphosate-resistant horseweed. In 2005, he lead the development of a glyphosate resistance and stewardship workshop in Indianapolis involving academic weed scientists from 11 states. At this meeting the current status of the issue in the U.S. was discussed and the group agreed to develop a series of extension publications and pursue funding for printing. Individual publications focus on general stewardship considerations, proper glyphosate use, and the biology and management of weeds that are resistant or tolerant to glyphosate. Dr. Johnson has organized subsequent meetings of this group, which occurred in September 2005 (Des Moines, IA), March 2006 (St. Louis, MO), and September 2006 (Bloomington, IL) to further the discussion on education efforts related to this topic. He was able to obtain funding from various life sciences companies (approx. $50,000) and was co-pi on a NCIPM extension proposal that was funded for $31,150 that will pay for printing approximately 300,000 copies of these publications. Working with the Purdue University Ag Communications Department, Dr. Johnson created a new publication series called the GWC (Glyphosate, Crops, and Weeds) series. All publications produced were or will be formatted and edited by the Purdue Ag Communications Department and posted at central website (glyphosateweedscrops.org). This website is the first site in the U.S.A. which is devoted to dissemination of information on glyphosate stewardship and resistance weeds by a Land Grant University. These publications will be distributed in all 13 North Central States, Pennsylvania, Delaware, and the Canadian Province of Ontario. Dr. Johnson received the PUCESA Special Award in 2007 for these efforts. Finally, Dr. Johnson's Extension efforts have been instrumental in raising awareness of glyphosate-resistance in weeds. In a recent phone survey of over 1150 growers in 6 states (IA, IL, IN, MS, NC, NE), 90% of Indiana growers were aware of the potential of weeds to develop resistance to glyphosate, compared to 84% of growers in other states. In addition 54% of the growers in Indiana were aware of specific glyphosate-resistant weeds in Indiana, compared with 35% of growers in other states.
Publications
- Barnes, J., B. Johnson*, K. Gibson, and S. Weller. 2004. Crop rotation and tillage system influence late-season incidence of giant ragweed and horseweed in Indiana soybean. Online. Crop Management doi:10.1094/CM-2004-0923-02-BR.
- Davis, V. M., K. D. Gibson, T. T. Bauman, S. C. Weller, and W. G. Johnson*. 2007. Influence of weed management practices and crop rotation on glyphosate-resistant horseweed population dynamics and crop yield. Weed Sci. 55:508-516.
- Kruger, G. K., V. M. Davis, S. C. Weller, and W. G. Johnson*. 2008. Response and survival of rosette-stage horseweed (Conyza canadensis) after exposure to 2,4-D. Weed Sci. 56:748-752.
- Westhoven, A. M., G. R. Kruger, C. K. Gerber, J. M. Stachler, M. M. Loux, and W. G. Johnson*. 2008. Characterization of selected common lambsquarters (Chenopodium album) biotypes with tolerance to glyphosate. Weed Sci. 56:685-691.
- Davis*, V. M., P. T. Marquardt, and W. G. Johnson. 2008. Volunteer corn in northern Indiana soybean fields is correlated to glyphosate-resistant corn adoption. Crop Management doi:10.1094/CM-2008-0721-01-BR .
- Davis, V. M., K. D. Gibson, T. T. Bauman, S. C. Weller, and W. G. ohnson*. 2008. A field survey to determine the distribution and frequency of glyphosate-resistant horseweed (Conyza canadensis) in Indiana. Weed Technol. 22:331-338.
- Davis, V. M., and W. G. Johnson*. 2008. Glyphosate-resistant horseweed emergence, survival, and fecundity in no-till soybean. Weed Sci. 56:231-236.
- Westhoven, A. M., J. M. Stachler, M. M. Loux, and W. G. Johnson*. 2008. Management of glyphosate-tolerant common lambsquarters (Chenopodium album) in glyphosate-resistant soybean (Glycine max). Weed Technol. 22:628-634.
- Westhoven, A. M., V. M. Davis, K. D. Gibson, S. C. Weller, and W. G. Johnson*. 2008. Field presence of glyphosate-resistant horseweed (Conyza canadensis) and common lambsquarters (Chenopodium album) and giant ragweed (Ambrosia trifida) biotypes with elevated tolerance to glyphosate. Weed Technol. 22:544-548.
- Gibson*, K. D., and W. G. Johnson. 2006. Crop rotation affects farmer perceptions of weed problems in corn and soybean weeds in Indiana. Weed Technol. 20:751-755.
- Johnson*, W. G. and K. D. Gibson. 2006. Glyphosate resistant weeds and resistance management strategies: An Indiana grower perspective. Weed Technol. 20:768-772.
- Gibson*, K.D., W.G. Johnson, and D. Hilger. 2005. Farmer perceptions of problematic corn and soybean weeds in Indiana. Weed Technol. 19:1065-1070.
- Johnson*, B., J. Barnes, K. Gibson, and S. Weller. 2004. Late season weed escapes in Indiana soybean fields. Online. Crop Management doi:10.1094/CM-2004-0923-01-BR.
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Progress 07/01/06 to 06/30/07
Outputs
OUTPUTS: In-field surveys, which directly estimate weed population densities, typically utilize either random or non-random field selection methods. We used both methods to characterize the distribution and frequency of glyphosate-resistant horseweed populations (Conyza canadensis) and other late-season soybean weed escapes and to develop a database for tracking weed shifts, control failures, and the presence of other herbicide-resistant biotypes over time in Indiana. In-field surveys were conducted in a total of 978 Indiana soybean fields during September and October of 2003, 2004, and 2005. Information from fields with horseweed was obtained from 158 sites (19%) sampled through a systematic random site selection method and 128 fields through a non-random site selection method. When present, horseweed seed was collected, germinated in the greenhouse, and rosettes 5 to 10 cm wide were sprayed with 1.72 kg ae/ha of glyphosate. Populations with less than 60% visual control at 28 days
after treatment were determined to be glyphosate-resistant. A selected subset of glyphosate-resistant populations was confirmed resistant by subsequent glyphosate dose response experiments. All populations in the subset with less than 60% visual control at the 1.72 kg ae/ha rate of glyphosate demonstrated R:S ratios of 4 to 110. Glyphosate-resistant populations were found in all regions of Indiana; however, the highest frequencies were in the Southeast region with 38% of fields sampled and only 1, 2, and 2% of fields sampled in the Northwest, Northeast, and Southwest regions, respectively. Over the last 3 years, these results have been disseminated in over 100 county-based Extension meetings targeted at growers, more than 20 field days, and more than 30 diagnostic training center events. In addition, the "biology and management of horseweed" publication was revised and an additional 20,000 copies were printed and distributed throughout the midwest.
PARTICIPANTS: Mark Loux - Extension Weed Scientist at Ohio State University conducted similar surveys and management studies in Ohio and co-authored the "biology and management of horseweed" publication. Kevin Gibson and Steve Weller - Weed Scientists at Purdue University collaborated with Johnson on the survey projects and the biology studies. Vince Davis - is a graduate student in Johnson's lab. Vince was responsible for much of the day to day work on the survey, and the greenhouse and field studies. The Indiana Soybean Association - provided some additional funding for all of the projects related to this grant proposal and additional funding to print the Extension publication titled "biology and management of horseweed". USDA CSREES NCIPM Competitive Grants Program - provided some additional funding to print copies of other publications in the Glyphosate, Weeds, and Crops series described below. Glyphosate Stewardship Working Group - In 2005, Johnson lead the development of a
glyphosate resistance and stewardship workshop in Indianapolis involving academic weed scientists from 11 states. At this meeting the current status of the issue in the U.S. was discussed and the group agreed to develop a series of extension publications and pursue funding for printing. Individual publications focus on general stewardship considerations, proper glyphosate use, and the biology and management of weeds that are resistant or tolerant to glyphosate. Dr. Johnson has organized subsequent meetings of this group, which occurred in September 2005 (Des Moines, IA), March 2006 (St. Louis, MO), and September 2006 (Bloomington, IL) to further the discussion on education efforts related to this topic. He was able to obtain funding from various life sciences companies (approx. $50,000) and was co-pi on a NCIPM extension proposal that was funded for $31,150 that will pay for printing approximately 300,000 copies of these publications. Working with the Purdue University Ag
Communications Department, Dr. Johnson created a new publication series called the GWC (Glyphosate, Crops, and Weeds) series. All publications produced were or will be formatted and edited by the Purdue Ag Communications Department and posted at central website (glyphosateweedscrops.org). This website is the first site in the U.S.A. which is devoted to dissemination of information on glyphosate stewardship and resistance weeds by a Land Grant University. These publications will be distributed in all 13 North Central States, Pennsylvania, Delaware, and the Canadian Province of Ontario.
TARGET AUDIENCES: Farmers and crop advisors - Johnson has spoken about horseweed biology and management at over 100 county based Extension meetings, field days and diagnostic training events over the last 3 years. In addition he has distributed over 20,000 copies of the horseweed publication at these meetings and by providing copies to county Extension educators, certified crop advisors, and retailers. Over 50,000 copies of this publication have been delivered throughout the midwest.
Impacts
Information gathered in this survey assisted in the development of applied research on control of this weed, as well as research into the biology and fitness of glyphosate-resistant populations compared to sensitive populations. In addition, we have focussed Extension educational efforts on the biology and management of glyphosate-resistant horseweed in southeast Indiana. The primary management tactics for this weed include the use of tillage, preplant 2,4-D, or soil applied herbicides. The use of 2,4-D or soil applied herbicides in soybeans has grown to about 30% of the acres, which is a substantial increase compared to 5 years ago when 10% or less of the acres were treated with these herbicides. Finally, we are using the database developed from this project to determine which fields to sample for the presence of glyphosate-resistant giant ragweed and common lambsquarters. To date, we have found glyphosate-resistant giant ragweed in 14 Indiana counties and problematic
common lambsquarter populations in 10 counties.
Publications
- Davis, V. M., K. D. Gibson, T. T. Bauman, S. C. Weller, and W. G. Johnson*. 2007. Influence of weed management practices and crop rotation on glyphosate-resistant horseweed population dynamics and crop yield. Weed Sci. 55:508-516.
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Progress 07/01/05 to 07/01/06
Outputs
This project was just initiated in the fall of 2005. I have recruited a graduate student who has begun sorting through the database and visiting fields that had glyphosate-resistant marestail and lambsquarter and giant ragweed escapes when sampled in 2003. Weed seed samples are being collected for herbicide resistance screening.
Impacts
We are investigating whether or not the presence of glyphosate resistant marestail can be used as an indicator species for other glyphosate tolerant weeds. If presence of glyphosate resistant marestail can be used as an indicator specie for other glyphosate tolerant weeds, we will have an early warning system in place for glyphosate resistant weeds. This will allow us to implement proactive extension programming to promote better management practices.
Publications
- No publications reported this period
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Progress 07/01/05 to 06/30/06
Outputs
We have found glyphosate-resistant giant ragweed in 10 counties with resistance ratios ranging from 2 to 7. We have found common lambsquarter populations that show resistance ratios of 2 to 4. Additional studies on the fitness characteristics of these biotypes has shown that they grow more rapidly in the early part of the growing season and begin reproductive growth earlier than sensitive populations. We are conducting management and demonstration trials in grower fields in Jay and Tippecanoe county to evaluate management practices for corn and soybean fields that have glyphosate-resistant or tolerant common lambsquarter and giant ragweed biotypes. A field day was held at the Jay county site in 2006, and at the Tippecanoe county site in 2007. The field days were attended by over 30 growers in those regions. We plan to conduct the management/demonstration trials again in 2007. Finally, we were continuing our work on the glyphosate stewardship publications and have
created a website to display and purchase the publications (see glyphosateweedscrops.org). The glyphosate stewardship working group met twice in 2006 (St. Louis, MO and Bloomington, IL) and once in 2007 (St. Louis, MO) to continue our discussion of this topic and work on publications. We have printed 5 of these to date, and have two ready to go the printer and the final two in the rough draft phase. See publication list to view the publications which have been printed.
Impacts
In a recent phone survey (manuscript will be submitted to Science) of over 1150 growers in 6 states (IA, IL, IN, MS, NC, NE), 90% of Indiana growers were aware of the potential of weeds to develop resitance to glyphosate, compared to 84% of growers in other states. In addition 54% of the growers in Indiana were aware of glyphosate-resistant weeds in Indiana, compared with 35% of growers in other states.
Publications
- Loux et al. 2006. Biology and Management of Horseweed. Purdue Univ. Coop. Ext. Pub. GWC-9.
- Zollinger et al. 2006. Biology and Management of Wild Buckwheat. Purdue Univ. Coop. Ext. Pub. GWC-10.
- Johnson et al. 2007. Biology and Management of Giant Ragweed. Purdue Univ. Coop. Ext. Pub. GWC-12.
- Curran et al. 2007. Biology and Management of Common Lambsquarter. Purdue Univ. Coop. Ext. Pub. GWC-11.
- Boerboom et al. 2006. Facts About Glyphosate Resistant Weeds. Purdue Univ. Coop. Ext. Pub. GWC-1.
- Hartzler et al. 2006. Understanding Glyphosate to Increase Performance. Purdue Univ. Coop. Ext. Pub. GWC-2.
- Johnson, W. G., K. D. Gibson, and S.P. Conley. Does weed size really matter? An Indiana grower perspective about weed control timing. Weed Technol. 21:542-546. (ARP manuscript no. 2006-17996)
- Gibson, K. D., and W. G. Johnson. 2006. Crop rotation affects farmer perceptions of weed problems in corn and soybean weeds in Indiana. Weed Technol. 20:751-755. (ARP manuscript no. 2005-17776)
- Johnson, W. G. and K. D. Gibson. 2006. Glyphosate resistant weeds and resistance management strategies: An Indiana grower perspective. Weed Technol. 20:768-772. (ARP manuscript no. 2005-17781)
- Gibson, K.D., W.G. Johnson, and D. Hilger. 2005. Farmer perceptions of problematic corn and soybean weeds in Indiana. Weed Technol. 19:1065-1070. (ARP manuscript no. 2005-17779)
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