I WILL KNOW THE ELEVEN HERBICIDE-RESISTANT WEEDS THAT THREATEN

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1 I WILL KNOW THE ELEVEN HERBICIDE-RESISTANT WEEDS THAT THREATEN

2 Know Your Weeds: The 11 Biggest Resistance Threats Herbicide resistance is real. And it s ominous. There are many weeds that are developing resistance to herbicides. But the weeds listed on these pages have taken resistance to whole new levels of risk. Which is why they are called The 11 That Threaten. Use the information in this guide to know more about them and why they are such a menace. Once you know their strengths and weaknesses, you can take action to minimize or eliminate their presence in your fields. For more information on The 11 That Threaten and other herbicide-resistant weeds, visit Herbicide Groups and Sites of Action Herbicide Groups provide a simple way of determining a herbicide s site of action. The site of action is the specific protein a herbicide binds to, 1 resulting in disruption of a physiological process 2 (mode of action) and plant death. Weed-management programs 3 that include multiple Herbicide Groups effective against 4 problem weeds are the first step in managing herbicide resistance. Herbicide Group 8 numbers are displayed on most herbicide labels. 9 This publication provides information on the Herbicide 10 Groups most commonly used in soybean production. 13 Also, the most problematic herbicide-resistant weeds 14 and the Herbicide Groups they have evolved resistance 15 to are displayed. 22 Site of Action Group Site of Action ACCase Inhibitors ALS Inhibitors Microtubule Inhibitors T1R1 AUXIN RECEPTORS Photosystem II Inhibitors LIPID SYNTHESIS INHIBITOR (not ACCase) EPSP Synthase Inhibitor Glutamine SYNTHETASE Inhibitor DITERPENE BIOSYNTHESIS INHIBITOR PPO Inhibitors Long-chain fatty acid Inhibitors Photosystem I Electron Diverter Product examples (Trade Name ) Assure II, Select Max Classic, Pursuit Prowl H 2 O, Treflan 2,4-D, Clarity, quinclorac atrazine, metribuzin, Basagran, Linex Far-Go Roundup (glyphosate) Liberty Command Flexstar, Cobra Dual, Harness Gramoxone (paraquat) 27 HPPD Inhibitors Callisto, Laudis

3 Waterhemp 01 11Eleven Common Waterhemp AKA: Amaranthus rudis Waterhemp Midwest, Plains 1 to 1.25 inches per day; rapid early-season growth allows seedlings to acquire more light than other weeds Emerges throughout growing season Can escape many pre-emergence herbicides and post-emergence applications without residuals Herbicide-resistance traits can transfer by pollen very quickly Major ability to infest fields; up to 1,000,000 seeds per plant; seeds remain viable in soil for up to four years Does not emerge from low soil depths Relatively short-lived in the soil seed bank (four to five years)

4 02 11Eleven Pigweed PALMER AMARANTH AKA: Amaranthus palmeri Palmer Pigweed South, Midwest, Lower Plains Up to 2.5 inches per day; rapid growth in all stages makes control with post-emergence herbicides exceedingly difficult Extremely competitive High reproductive capacity; up to 1,000,000 seeds per plant Herbicide-resistance traits can transfer by pollen Extended germination period Does not emerge from low soil depths Short-lived in the soil seed bank (four to five years)

5 Marestail 03 11Eleven Horseweed AKA: Conyza canadensis Marestail, Canada Fleabane Midwest, East, South Emerges from late March through June and from late summer through late fall Up to 200,000 seeds per weed Approximately 80 percent of seeds will germinate right off the plant Windblown seeds disperse easily across great distances Doesn t tolerate soil disturbance, such as deep tillage Doesn t tolerate shading from crop canopy

6 04 11Eleven Giant Ragweed Giant Ragweed AKA: Ambrosia trifida Horseweed Midwest, Plains, Midsouth Emerges from up to 5 inches deep in soil Very competitive with Midwest crops Herbicide-resistance traits can transfer by pollen Seed does not persist if lying on soil surface (long-term no-till) 2 9

7 Common Ragweed 05 11Eleven Common Ragweed Ambrosia artemisiifolia South, Midwest Emerges from up to 5 inches deep in soil Very competitive with Midwest crops Herbicide-resistance traits can transfer by pollen Seed does not persist if lying on soil surface (long-term no-till)

8 06 11Eleven Lambsquarters Common Lambsquarters Chenopodium album Midwest Germinates and emerges early in the spring; easy to control with residual pre-emergence herbicides Difficult to control with post-emergence herbicides Controlled effectively by many soil-applied herbicides 2 5

9 07 11Eleven Kochia Kochia Kochia scoparia Plains Shallow germination; early-season and extended germination High seed producer; tumbleweed seed dispersal Drought tolerant; salt tolerant Poor competitor in wet, humid environments Short seed life

10 08 11Eleven Italian Ryegrass Italian Ryegrass Lolium multiflorum Northwest, South Winter annual Resistance has developed to many of the commonly used herbicides Can move via contaminated wheat and cover crop seed Poor winter hardiness Seed normally persist on the plant without falling to the ground Barnyard grass Echinochloa crus-galli South, Lower Midwest Summer annual Difficult to control with most herbicides Tolerant of saturated soils and flooding Seed spreads by waterfowl and surface water movement Does not emerge from low soil depths Barnyard Grass 09 11Eleven

11 10 11Eleven Johnsongrass Johnsongrass Sorghum halepense Plains, South, Lower Midwest Perennial growth habit Multiple herbicide applications needed for effective control Can spread by seed or underground rhizomes Problematic in areas where soil does not freeze Aggressive tillage can weaken stand Giant Foxtail Setaria faberi Midwest Summer annual Very competitive with Midwest crops Seed germinates on surface of ground Does not emerge from low soil depths Giant Foxtail 11 11Eleven

12 01 Common Waterhemp 02 Palmer Amaranth 03 Horseweed 04 Giant Ragweed 05 Common Ragweed 06 Common Lambsquarters 07 Kochia 08 Italian Ryegrass 09 Barnyard Grass 10 Johnsongrass 11 Giant Foxtail Brought to you by the soy checkoff. For more information and links to additional resources, visit Take action is supported by BASF; Bayer; DuPont; Dow; Monsanto; Syngenta; and corn, cotton, sorghum, soy and wheat organizations. The United Soybean Board neither recommends nor discourages the implementation of any advice contained herein, and is not liable for the use or misuse of the information provided United Soybean Board