Weed management for Minnesota crops

Annual weeds

Grass weeds:

• Barnyardgrass.
• Large crabgrass.
• Green, giant and yellow foxtail.
• Wild oat.
• Fall panicum.
• Wild proso millet.

Broadleaf weeds:

• Amaranth family: Waterhemp, Palmer amaranth and redroot pigweed.
• Giant and common ragweed.
• Common cocklebur.
• Common lambsquarters.
• Velvetleaf and more.

Perennial weeds

• Jerusalem artichoke
• Field and hedge bindweeds
• Yellow nutsedge
• Quackgrass
• Canada thistle and perennial sowthistle.

Weed identification tools

• Weed image search tool from the Strand Memorial Herbarium. Plants are searchable by common names, plant families or genera.

• Archived PDF guide

• Seedling identification key – A step-by-step key to identify seedlings using plant characteristics. Includes both broadleaf and grass seedlings. (1999)

• Herbicide mode of action and sugarbeet injury symptoms — An in-depth look at eight herbicide families, their modes of action, factors that influence their effectiveness, and injury symptoms.
• Herbicide classification chart — Groups herbicides by sites of action to help you maintain greater herbicide diversity and delay the development of resistance. Developed by Take Action: Herbicide-Resistance Management.

Applying herbicides

• Herbicide-resistant traits in Minnesota and North Dakota — This guide clarifies which herbicides can be applied to various trait packages for our major crops.
• How to calculate herbicide rates and calibrate herbicide applicators — Calculations for determining how much herbicide you need, plus calibration how-tos for sprayers and granule applicators.  
• Managing risk when using herbicides and cover crops — How to successfully use herbicides when incorporating cover crops into corn and soybean systems. Research on sensitivity to herbicide carryover and weed-control strategies.

Archived PDF chart

• Diversification strategies and crop rotation intervals for corn and soybean herbicides — Herbicide rotation intervals and diversification strategies for corn and soybeans, 2021.

Off-target dicamba movement

In 2017, low-volatility formulations of dicamba were released for use with dicamba-tolerant soybean. Non-tolerant soybeans are extremely sensitive to this chemical. Despite the new formulations, dicamba injury to non-target soybeans was widely reported in Minnesota and several other states.

• Understanding dicamba’s wayward ways
• Symptoms of dicamba exposure in soybean
• Effect of dicamba exposure on yield

See the Minnesota Department of Agriculture for Minnesota-specific Dicamba requirements.

Spray drift

• How to avoid pesticide drift — Strategies for nozzle selection, buffer zones, and wind speeds. Legal implications. How to report issues.

Videos

• Herbicide spray drift demonstration (2014; 06:59) — This video shows the off-target movement of glyphosate in oat plots using six nozzle types with droplet sizes ranging from fine to ultra-coarse.  
• Why temperature inversions are important (2017; 03:07) — This video addresses what temperature inversions are, when they occur, how to know if they’re occurring, and why they’re important when deciding if it’s the right time to spray. Look at current and predicted wind speed and rainfall conditions when deciding to spray.

Losing herbicide options significantly affects crop producers. Fortunately, there are things you can do to prevent and manage herbicide-resistant weeds.

• Guide to preventing herbicide-resistant weeds in Minnesota  – How resistance develops, management strategies, and herbicide lists by sites of action.

• How to test your waterhemp population for PPO-inhibiting herbicide resistance
  A testing service for crop producers, plus details about the prevalence of herbicide-resistant waterhemp in Minnesota.
• Pre-emergence (PRE) herbicides  – How pre-emergence (PRE) herbicides affect weed control and soybean yield in Minnesota. On-farm research on PRE vs. postemergence-only herbicide applications.
• Using layered residual herbicides to manage waterhemp in soybean

Archived PDF guide

Corn and soybean: Herbicide diversification strategies  – Pre- and postemergence herbicide diversification options and rotation intervals for glyphosate-resistant corn and soybeans. Updated January, 2021.