2020 In-Season Dicamba Alternatives: What to Expect

If you’re in one of the states that has ceased dicamba applications, or you’ve decided not to take on the potential liability risk by spraying the herbicide after the 9th Circuit Court vacated the federal label, you still need to manage weeds in fields where you planned on spraying the herbicide. The problem is the three herbicide group alternatives–Group 2, 9 and 14–all have known weed resistance.

A tell-tale sign of resistance is just one or two specific weed species emerging after herbicide application—application failure means everyone can grow, resistance means just the resistant weeds thrive.

Be ready to scout, know what weeds to watch for and have a backup plan in mind.

First, you need to scout to determine what’s actually going on in fields. Use practical steps to figure out if it’s weed resistance that requires a different approach, or if it’s sprayer error or another issue.

• Application error: look for streaks from clogged nozzles or where you didn’t get adequate overlap, according to experts at NuFarm.
• Rain activation failure: some herbicides require rain to activate them, so if you don’t get adequate rain they might not work. FMC experts recommend using a rotary hoe or another mechanical method to activate.
• pH challenges: if nothing else makes sense, and you’re seeing a wide variety of species instead of just one or two, double check the herbicide’s label and compare it to your soil’s pH to make sure they play well together.

Globally, group 2, ALS herbicides, have more than 160 documented cases of resistance; group 9, ESPS inhibitor herbicides (glyphosate), have 48 documented cases of resistance; and group 14, PPO herbicides, have 13 documented resistance cases.

Here’s the breakdown of weeds with well-documented resistance in at least one state in the U.S. according to the International Survey of Herbicide Resistant Weeds, updated June 8, 2020.

• Group 2, ALS herbicides:
  • Livid Amaranth
  • Smooth Pigweed
  • Palmer Amaranth
  • Powell Amaranth
  • Spiny Amranth
  • Tall Waterhemp
  • Common Ragweed
  • Giant Ragweed
  • Eared Redstem
  • Redstem
  • Mayweed Chamomile
  • Wild Oat
  • Japanese Brome
  • Cheat (Rye Brome)
  • Downy Brome (Cheatgrass)
  • Smallseed Flaxfalse
  • Spotted Splurge
  • Common Lambsquarters
  • Horseweed
  • Annual Sedge
  • Smallflower Umbrella Sedge
  • Yellow Nutsedge
  • Rice Flatsedge
  • Flixweed
  • Junglerice
  • Barnyardgrass
  • Bushy Wallflower
  • Common Sunflower
  • Marshelder
  • Kochia
  • Prickly Lettuce
  • Henbit Deadnettle
  • Perennial Ryegrass
  • Italian Ryegrass
  • Red Rice
  • Annual Bluegrass
  • California Arrowhead
  • Russian-Thistle
  • Ricefield Bulrush
  • Feral Rye
  • Giant Foxtail
  • Yellow Foxtail
  • Green Foxtail
  • Giant Green Foxtail
  • Prickly Sida
  • Wild Mustard
  • Eastern Black Nightshade
  • Spiny Sowthisle
  • Shattercane
  • Johnsongrass
  • Common Chickweed
  • Common Cocklebur
• Group 9, ESPS Inhibitors (Glyphosate)
  • Palmer Amaranth
  • Spiny Amaranth
  • Tall Waterhemp
  • Common Ragweed
  • Giant Ragweed
  • Hairy Fleabane
  • Horseweed
  • Junglerice
  • Goosegrass
  • Common Sunflower
  • Kochia
  • Italian Ryegrass
  • Rigid Ryegrass
  • Ragweed Parthenium
  • Annual Bluegrass
  • Russian-Thistle
  • Johnsongrass
• Group 14, PPO Inhibitors
  • Palmer Amaranth
  • Tall Waterhemp
  • Common Ragweed
  • Goosegrass

The loss of dicamba due to the 9th Circuit Court of Appeals’ ruling does limit what you can use. Understand the limitations and do you best to control weeds before they go to seed.

Read more about the recent dicamba Court mandate:

States Ask EPA for Clarity on Dicamba, State’s Rights to Sell

Non-Dicamba Options for Dicamba-Tolerant Soybeans

Xtendimax, Engenia and FeXapan Sales and Application “Paused”