Weed of the Month: Waterhemp

waterhempThe battle against herbicide resistance continues as waterhemp persistently challenges growers and forces them to rethink their weed control programs. In the past 25 years, waterhemp has grown resistant to six classes of herbicides and threatens to resist various modes of action.

  • Common name: Tall waterhemp
  • Scientific name: Amaranthus tuberculatus1
  • Cotyldons: egg-shaped2
  • Leaf shape: long and narrow, smooth stems and leaves2
  • Reproduction: dioecious (separate male and female plants)2
  • Flowers: structure near top of plant and tips of branches2

Fast facts

  • History: Herbicide-resistant waterhemp was first discovered in 1993 in Iowa and it has spread across the Midwestern states within the past 20 years.3
  • Origin: Waterhemp is native to North America; however, waterhemp was not a weed found in crop fields like other pigweed species. Researchers believe waterhemp may have taken traits from a different Amaranthus species and moved from marshes to fields.1
  • Variations: There are two variations of waterhemp. One variation (Amaranthus tuberculatus var. rudis) is found west of the Mississippi River; the other variation (Amaranthus tuberculatus var. tuberculatus) is found east of the Mississippi.1
  • Fast-growing: Waterhemp grows quickly. A plant can grow 1-1¼ inches in one day.4
  • Many seeds: Waterhemp can produce about 250,000 seeds per plant and up to 1 million seeds without competition.4
  • Long-lasting seeds: Waterhemp seeds can germinate many years after they are produced. Some research shows that 12% of waterhemp seeds could germinate after four years.4

Control tips

  • Scout early — and often. Waterhemp looks very similar to Palmer amaranth early in its growth; however, there are differences. Look for longer, more lance-shaped leaves than pigweed species.5
  • Use multiple modes of action through various herbicide options. Layer residual herbicides to target different areas of the plant.5
  • Change row spacing. Narrower rows help crops get to canopy and overpower weeds before they grow too large to actively control.5
  • Use tillage, if appropriate. Waterhemp seeds cannot germinate unless they are in the top layer of soil. However, growers must be cautious of erosion.5
  • Utilize crop rotation. It can allow growers to change up herbicides and modes of action to help fight weed resistance.5

States with Herbicide-Resistant Waterhemp by Crop3

States with Waterhemp Resistant to Glyphosate3

Corteva Agriscience offers the following weed control solutions:

Corn Herbicides

DuPont Cinch® ATZ herbicide
Durango® DMA® herbicide
Elevore® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One® herbicide, as part of the Enlist weed control system
FulTime® NXT herbicide
Keystone® LA NXT herbicide
Keystone® NXT herbicide
DuPont Realm® Q herbicide
Resicore® herbicide
SureStart® II herbicide

Soybean Herbicides
Durango® DMA® herbicide
Elevore herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One® herbicide, as part of the Enlist weed control system
DuPont EverpreX® herbicide
FirstRate® herbicide
Sonic® herbicide
Surveil® herbicide
DuPontAfforia® herbicide
DuPontEnlite® herbicide
DuPont™ FeXapan™ herbicide Plus VaporGrip® Technology
DuPont Trivence® herbicide


Sources:

1Iowa State University, Extension and Outreach. 2019. Waterhemp. a ‘friendly’ native evolves into the Cornbelt’s worst weed problem. https://crops.extension.iastate.edu/blog/bob-hartzler/waterhemp-friendly-native-evolves-cornbelts-worst-weed-problem
2University of Minnesota Extension. Annual broadleaf weeds. https://extension.umn.edu/weed-identification/annual-broadleaf-weeds#amaranth-family-id-waterhemp-palmer-amaranth-and-redroot-pigweed-838061
3International Survey of Herbicide Resistant Weeds. Herbicide resistant tall waterhemp globally. http://weedscience.org/Summary/Species.aspx
4United Soybean Board. 2018. Waterhemp management in soybeans. https://iwilltakeaction.com/uploads/files/54403-01-ta-factsheet-waterhemp-update-lr_1.pdf
5AGDAILY. 2018. Corteva Agriscience: five tips for fighting off waterhemp. https://www.agdaily.com/crops/corteva-agriscience-five-tips-waterhemp/

™®Afforia, Cinch, DMA, DuPont, Durango, Elevore, Enlist, Enlist Duo, Enlist One, Enlite, EverpreX, FeXapan, FirstRate, FulTime, Keystone, Realm, Resicore, Sonic, SureStart, Surveil and Trivence are trademarks of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. VaporGrip® is a registered trademark of and used under license from Monsanto Technology LLC. Cinch ATZ, FulTime NXT, Keystone LA NXT and Keystone NXT are Restricted Use Pesticides. FeXapan herbicide Plus VaporGrip Technology is a Restricted Use Pesticide. For retail sale to and use only by Certified Applicators and only for those uses covered by the Certified Applicator’s certification. Cinch ATZ, Durango DMA, Elevore, FeXapan herbicide Plus VaporGrip Technology, FulTime NXT, Keystone LA NXT, Realm Q, Resicore, Sonic, SureStart II and Surveil are not registered for sale or use in all states. Keystone NXT is not available for sale, distribution or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. EverpreX is not registered in all states. See your Corteva Agriscience retailer or representative for availability in your state. Enlist Duo and Enlist One herbicides are not registered for sale or use in all states or counties. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use in Enlist crops. Consult Enlist herbicide labels for weed species controlled. Always read and follow label directions. © 2020 Corteva.