Iowa farmers, take note: the presence of dicamba-resistant waterhemp has been confirmed in two separate populations within the state, as reported by Bayer. Samples collected in Scott County in 2021 and Marshall County in 2022 have raised concerns among the agricultural community.
Although this marks the first instance of plant growth regulator (HG 4) resistance in waterhemp in Iowa, other states have previously identified HG 4-resistant waterhemp in their regions. Nebraska documented these resistant populations in 2009, followed by Illinois in 2016 and Missouri in 2018.
While there's no need for alarm, this discovery serves as a timely reminder that proactive management strategies are vital in addressing this evolving weed threat. Waterhemp has a notorious ability to swiftly adapt to herbicide control methods, emphasizing the necessity of diversifying control approaches, including herbicides, mechanical methods, and cultural practices.
Here are some recommended best practices to slow the development of dicamba-resistant waterhemp:
• Tailor Herbicide Programs: Choose an herbicide program that aligns with the specific weed species present in each field.
• Effective Residual Herbicides: Apply full rates of effective residual herbicides and plant crops in weed-free seedbeds.
• Overlapping Residual Herbicides: Incorporate overlapping residual herbicides in postemergence applications to extend waterhemp control.
• Timely Applications: Ensure herbicide applications are made on schedule and adhere to label instructions regarding adjuvants, nozzles, application volume, etc.
• Regular Field Scouting: Assess weed control effectiveness 7-10 days after postemergence herbicide applications.
• Diverse Weed Management Tactics: Employ a variety of weed management strategies, encompassing chemical, mechanical, and cultural methods. Techniques such as narrow row spacing, cover crops, crop rotation, and tillage have proven effective in suppressing waterhemp.
• Address Weed Escapes: Prevent weed seed production by managing weed escapes before they can set seeds. This reduces future weed populations and the spread of resistance traits.
• Minimize Seed Influx: Manage field edges and maintain clean equipment to prevent the introduction of weed seeds from problematic fields into clean ones.
If you suspect dicamba-resistant waterhemp in your fields, don't hesitate to report it to Meaghan Anderson, Iowa State University Extension and Outreach field agronomist. Early detection and reporting play a crucial role in slowing the spread of this resistant weed.
Here are some additional strategies for managing dicamba-resistant waterhemp:
• Avoid Dicamba Usage: Steer clear of dicamba herbicides in fields where dicamba-resistant waterhemp has been identified.
• Use Dicamba Cautiously: If dicamba application is unavoidable, stick to the lowest labeled rate and meticulously follow all label directions.
• Rotate Herbicides: Rotate dicamba with other herbicide groups to prevent resistance development.
• Sustained Vigilance: Continuously scout your fields for waterhemp and promptly address any escapes.
By adopting these best management practices, farmers can contribute to slowing the progression of dicamba-resistant waterhemp and safeguard their crops. Vigilance and diversification are key to preserving the productivity of Iowa's farmlands.
Categories: Iowa, Crops