Problem Weed Control in Field Crops

Table of Contents

Canada Thistle in Winter Barley


The information presented here intended to provide growers with control options for problematic weed species in corn, soybeans and wheat.

To find information on a particular weed species, you can either search by "common weed name" (i.e. Dandelion) or "scientific weed name" (i.e. Taraxacum officinale). Either way you will be directed to a list of species included in this document.


The content in this publication is for informational purposes only. By providing this information, the University of Guelph, it's employees or agents, Agriculture and Agri-food Canada, and the Ontario Ministry of Agriculture and Food do not offer any warranty or guarantee, nor do they assume any liability for any crop loss, animal loss, health, safety or environmental hazard caused by the use of a pesticide mentioned in this publication.

The use of Trade names in this publication is for the user's convenience only. It is neither an endorsement of a particular product nor a suggestion that similar products are ineffective.

There are a number of herbicides referred to in this publication which may not be currently registered. Always follow label directions when applying herbicides.

Search by Common Weed Name

Weed species are listed in alphabetical order by the main common name. For example, if you wanted to find information on "Spreading atriplex" it would be listed as Atriplex, spreading.

Search by Scientific Weed Name

Weed species are listed in alphabetical order by genus.

List of Contributors

Dr. Al HamillDr. Al Hamill

Research Scientist, Weed Management
Greenhouse Processing and Crops Research Centre, Harrow ON.

Research Interests:
Current research concentrates on the integration of weed management into conventional and no-till (conservation till) production systems for corn, soybeans, tomatoes and sugarbeets for Southwestern Ontario. He also plays an integral role in the Minor Use registration for numerous herbicide treatments for use in tree fruit new plantings, mature orchards, tomatoes and seed corn.

Honours and Awards

2002 - President of the Weed Science Society of America
1999 - Named to the Essex County "Hall of Fame" for contributions to local and national agriculture

Peter SikkemaPhoto of Peter Sikkema

Assistant Professor
University of Guelph, Department of Plant Agriculture Ridgetown , ON.

Research Interests:
Evaluation of new herbicides for use in field and horticultural crops. Determine the spectrum of weeds controlled and crop safety. Evaluate weed management programs in herbicide resistant crops such as Roundup Ready corn and Roundup Ready soybeans. Develop weed management strategies for the control of problem weeds in corn, soybeans and wheat. Determine the effect of crop row width and seeding density on weed management. Determine the impact of long-term weed management systems on weed shifts.

Photo of Clarence SwantonClarence J. Swanton

University of Guelph, Department of Plant Agriculture

Research Interests:
My research goal is to facilitate the integration of ecological principles into crop production systems. My major area of research has been to design and implement integrated weed management systems for field and horticultural crops grown in Ontario. Selected areas of study have included weed and crop modelling, weed biology and ecology, economics of weed management and managing weeds with herbicides.

François J. Tardif

Photo of Francois TardifAssistant Professor
University of Guelph, Department of Plant Agriculture

Research Interests:
My main interest is currently in the understanding of herbicide resistance in weeds. This includes topics such as:

  • Characterisation of new cases
  • Development of diagnostic tools
  • Understanding the effect of resistance mutations on fitness
  • Developing management programs

Susan WeaverPhoto of Susan Weaver

Weed-Crop Ecologist, Greenhouse Processing and Crops Research Centre, Harrow ON.

Research Interests:
My research focuses on weed biology and ecology, and the development of integrated weed management systems in field crops. We conduct field and laboratory experiments to determine seed germination requirements, emergence patterns and seed production of different weed species in relation to crop management practices. Another objective is to quantify crop yield losses and establish economic thresholds for various weed species in soybeans and corn. This has led to the release of decision support software for weed management in these crops

Mike CowbroughPhoto of Mike Cowbrough

Weed Management Lead Ontario Ministry of Agriculture and Food - Guelph, ON

My goal is to identify the major weed management issues facing the Ontario Grower and then work with our awesome team of weed researchers to provide practical, economical and environmentally responsible solutions.


Field Technicians

Researchers at the University of Guelph and Agriculture and Agrifood Canada are fortunate to have an amazing team of field technicians. Without them, the field work would simply not get done at the high level that it does.

  • Dave Bilyea - Ridgetown Research Station
  • Kevin Chandler - Elora and Woodstock Research Station
  • Kerry Cheney - Ridgetown Research Station
  • Todd Cowan - Huron Park Research Station
  • Yvonne McLellan - Ridgetown Research Station
  • Kris McNaughton - Ridgetown Research Station
  • Christy Shropshire - Ridgetown Research Station
  • Peter Smith - Elora and Woodstock Research Station
  • Josh Vyn - Ridgetown Research Station
  • Mac Whaley - Greenhouse and Processing Crops Research Centre - Harrow

Weed Photographs - References:

We would like to acknowledge the following sources for the photographs shown throughout this document:

  • 1000 Weeds of North America - Illustrated CD

An amazing database of 1000 weeds found throughout North America. This interactive CD is very easy to use, has numerous colour photographs and will also direct you to page numbers of the most popular weed indentification books in order to get more information. To order this CD visit the XID Services website.

For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047