Navjot Singh, Graduate student, and Debalin Sarangi, Extension weed scientist
Herbicide-resistant weeds are threatening agronomic crop production in Minnesota (Figure 1). In 2020, we received about 30 waterhemp samples - mostly from southern MN - and the greenhouse resistance screening results showed that the majority of waterhemp populations were resistant to ALS-inhibiting herbicides (e.g., Pursuit, Raptor, and Classic) and glyphosate.
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Figure 1. Waterhemp plant surviving Enlist One application at 6 pt/A after 28 days after treatment in the greenhouse. |
The results also showed that 14 and 15% of waterhemp populations were resistant to atrazine and PPO inhibitors (e.g., Flexstar), respectively. If at least 40% of plants survive a 3X labeled dose of a certain herbicide, we consider that population to be resistant.
Two populations from Carver and Olmsted County showed resistance to four herbicide sites of action, significantly reducing herbicide choices for farmers (Figure 2). These populations have survived the 3X application of glyphosate, Raptor, Atrazine, and Flexstar or Callisto (a HPPD inhibitor).
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Figure 2. Distribution of multiple herbicide-resistant waterhemp populations in Minnesota. |
In three populations, 7 to 14% of waterhemp plants have survived the 3X dose of 2,4-D-choline (Enlist One), showing that the less-sensitive individuals to 2,4-D are present in Minnesota (Figure 1). Therefore, a diversified management approach should be taken to slow down the resistance evolution.
Seed samples requested
Please follow the steps below for sample collection and submission:- Select the fields with lower than expected weed control from herbicide applications (avoid sampling plant escapes due to lack of spray coverage)
- Collect the seedheads from at least 10 mature (black color seeds), female waterhemp plants, or 20 mature (brown seeds) ragweed plants and place the samples in paper bags. DO NOT mix the seeds of different species – please bag them separately!
- Fill out this submitter’s form and send it along with the samples.
- The samples can be mailed directly to the UMN’s St. Paul campus:
- Attn: Debalin Sarangi
411 Borlaug Hall
1991 Upper Buford Circle
St. Paul, MN 55108
Questions?
Any questions or concerns should be directed to:Dr. Debalin Sarangi, Extension Weed Scientist
Email: dsarangi@umn.edu
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