Characterization and Management of Herbicide-Resistant Weeds in Indiana
Sustainable Production
Field management Nutrient managementSoil healthTillageYield trials
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Bryan Young, Purdue University
Co-Principal Investigators:
Bill Johnson, Purdue University
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

The use of glyphosate as the primary weed management tool in soybeans has resulted in widespread weed resistance. Glyphosate-resistant waterhemp, Palmer amaranth, giant ragweed, and horseweed have increased and the frequency of multiple herbicide resistance beyond glyphosate continues to be a challenge in gaining effective control. This research is focused on improving weed management in soybeans by characterizing the extent of herbicide-resistant weed biotypes and developing management strategies for these problematic weeds. Objectives include documenting the distribution of glyphosate-resistant weeds; developing weed management strategies; and characterizing the difference the response to glyphosate between two giant ragweeds with different resistance mechanisms.

Key Benefactors:
farmers, agronomists, ag retailers, applicators, Extension specialists

Information And Results
Final Project Results

refer to uploaded report

View uploaded report PDF file

The lab provided a screening service for suspected herbicide resistance in waterhemp, Palmer amaranth, and giant ragweed through the Purdue Plant Diagnostic Lab during the 2016 field season. Waterhemp was the primary weed of concern in 2016 for the samples submitted to our lab for resistance screening, with some giant ragweed samples and no Palmer amaranth samples submitted. Waterhemp was also the most common weed species submitted for resistance screening in 2015, which cements waterhemp as the greatest developing weed resistance problem in Indiana.

Field research experiments designed to identify practices, herbicide products, herbicide strategies, or soybean traits that would improve weed management were conducted on herbicide-resistant waterhemp, giant ragweed, Palmer amaranth, and horseweed (marestail) in 2016. These field trials were conducted by Purdue University and collaborating investigators (Drs. Mark Loux and Aaron Hager) at The Ohio State University and the University of Illinois. Each year, we conduct over 50 trials at these sites and the results are either shared directly with clientele or synthesized and delivered to clientele at numerous venues and through different media outlets (see Communication section below for more details). Some research highlights include: the inconsistency of auxin herbicides (2,4-D and dicamba) for control of glyphosate-resistant horseweed when used as the sole means of control; the importance of application timing for both residual (close to period of peak emergence) and foliar (weed size under 4 inches) active herbicides for all four of these problematic weed species; and the potential for reduced herbicide activity when applying postemergence herbicides with extremely large spray droplets that may reduce spray coverage on target weeds. Overall, the greatest weed challenges arise when the herbicide applications are performed later than desired, as once these problematic weeds gain an advantage it can be nearly impossible to regain control to satisfactory levels for the remainder of the growing season. The results of this field research were delivered through various formats with clientele including the “Take Action” website sponsored by the United Soybean Board and the 2017 Weed Control Guide for Ohio, Indiana, and Illinois, in addition to other outreach activities.

Giant ragweed is among the most competitive summer annual weeds in corn and soybean production. Difficulty in controlling giant ragweed is exacerbated by the evolution of herbicide-resistant (HR) biotypes to both ALS-inhibiting herbicides and glyphosate. Glyphosate resistance (GR) in giant ragweed is unique as there exist two distinct phenotypic responses following application. The rapid response (RR) biotype displays a lesion-causing oxidative burst (rapid necrosis) in mature leaves in as little as two hours after treatment and quickly results in leaf desiccation, thus restricting glyphosate translocation. The non-rapid response (NRR) biotype of giant ragweed exhibits slightly chlorotic leaves and stunted plant growth (similar to glyphosate-resistant marestail response). Both biotypes resume normal growth within a week.
Glyphosate-resistant giant ragweed was found in 36 counties in Indiana compared to only 14 counties in a 2008 survey.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.