Weed Calendar for the Corn Belt

The differences in emergence characteristics of weed species are one of the reasons why weed management is such a difficult task. Knowing when weeds emerge can help improve weed management systems by increasing scouting efficiency and help determine optimum weed control tactic timing (seedbed prep, herbicide application, cultivation, etc). 

 

Weed emergence sequence of common troublesome annual weed species in the Corn Belt growing region. 

Identification 

Grasses 
Annual bluegrass. Photo courtesy of Shawn Wright, University of Kentucky, Bugwood.org. Annual bluegrass. Photo courtesy of Shawn Wright, University of Kentucky, Bugwood.org.
Downy brome. Downy brome.
Large crabgrass collar region. Photo courtesy of Steven Gower. Large crabgrass collar region.
Large crabgrass seedhead.Photos courtesy of Steven Gower. Large crabgrass seedhead.
Wooly cupgrass. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org. Wooly cupgrass. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org.
Barnyardgrass. Photos courtesy of Bruce Ackley, The Ohio State University and Howard F Schwartz, Colorado State University, Bugwood.org. Barnyardgrass. Photos courtesy of Bruce Ackley, The Ohio State University and Howard F Schwartz, Colorado State University, Bugwood.org.
Barnyardgrass. Photos courtesy of Bruce Ackley, The Ohio State University and Howard F Schwartz, Colorado State University, Bugwood.org. Barnyardgrass. Photos courtesy of Bruce Ackley, The Ohio State University and Howard F Schwartz, Colorado State University, Bugwood.org.
Green foxtail. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org. Green foxtail. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org.
Giant foxtail. Photo courtesy of John D. Byrd, Mississippi State University, Bugwood.org. Giant foxtail. Photo courtesy of John D. Byrd, Mississippi State University, Bugwood.org.
Yellow foxtail. Photo courtesy of Howard F. Schwartz, Colorado State University, Bugwood.org.   Yellow foxtail. Photo courtesy of Howard F. Schwartz, Colorado State University, Bugwood.org.
Goosegrass. Photo courtesy of John D. Byrd, Mississippi State University, Bugwood.org.  Goosegrass. Photo courtesy of John D. Byrd, Mississippi State University, Bugwood.org.
Fall panicum.  Fall panicum.

 

Broadleaves
Horseweed (marestail). Horseweed (marestail).
Wild mustard. Photo courtesy of Steven Gower. Wild mustard.
Shepherd’s purse. Photo courtesy of Steven Gower. Shepherd’s purse.
Purple deadnettle (left) and henbit (right). Purple deadnettle (left) and henbit (right).
Wild carrot. Photo courtesy of Ansel Oomen, Bugwood.org Wild carrot. Photo courtesy of Ansel Oomen, Bugwood.org
Common lambsquarters. Common lambsquarters.
Eastern black nightshade. Eastern black nightshade.
Pennsylvania smartweed. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org. Pennsylvania smartweed. Photo courtesy of Bruce Ackley, The Ohio State University, Bugwood.org.
Palmer amaranth. Photos courtesy of Stephen Gower. Palmer amaranth.
Palmer amaranth. Photos courtesy of Stephen Gower. Palmer amaranth.
Common waterhemp seedlings. Courtesy of Stephen Gower. Common waterhemp seedlings.
Common waterhemp stem Common waterhemp stem
Morningglory species (ivyleaf morningglory pictured). Photo courtesy of Stephen Gower. Morningglory species (ivyleaf morningglory pictured).
Common ragweed. Common ragweed.
Giant ragweed. Photo courtesy of Stephen Gower. Giant ragweed. Photo courtesy of Stephen Gower.
Redroot pigweed. Photo courtesy of Stephen Gower. Redroot pigweed. Photo courtesy of Stephen Gower.
Velvetleaf. Velvetleaf.

Sources:

Aneson, N., Striegel, S. and Werle, R. Giant ragweed. Grow IWM. http://growiwm.org.

Bradley K. 2018. Morning glory management in soybean. Take Action Herbicide Resistance Management. Http://iwilltakeaction.com.  

Curran, W.S. and Klodd, A. 2014. Invasive pigweeds: Palmer amaranth and waterhemp. Penn State Extension. http://extension.psu.edu.

Doll, JD. 2001. Knowing when to look for what: Weed emergence and flowering sequences in Wisconsin. Department of Agronomy. UW-Madison Wisconsin. http://extension.soils.wisc.edu.  

Hartzler, RG. 2008. Relative emergence sequence for weeds of corn and soybean. Iowa State University. http://www.extension.iastate.edu/.  

Pittman, K. Horseweed. Grow IWM. http://growiwm.org.

Sprague, C. 2020. Palmer amaranth management in soybeans. Take Action Herbicide Resistance Management. http://iwilltakeaction.com.

Steckel, L. 2019. Barnyardgrass management in soybeans. Take Action Herbicide Resistance Management. http://iwilltakeaction.com.

 

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