PLNT*6210 Herbicide Activity

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The following description is for the course offering in Fall 2019 and is subject to change. It is provided for information only. The course outline distributed to the class at the beginning of the semester describes the course content and delivery, and defines the methods and criteria to be used in establishing the final grades for the course.

This course provides a comprehensive study of the major herbicide groups used in Ontario. The various herbicide groups will discussed under the following topics: herbicide uptake and translocation, herbicide mode of action, herbicide selectivity, weeds controlled and crop injury.


Teaching Assistant:


Credit Weight:


Course Level:

  • Graduate

Academic Department (or campus):

Department of Plant Agriculture


Ridgetown Campus (video conference to Guelph campus)

Semester Offering:

  • Fall

Class Schedule and Location:

Please refer to Web Advisor for class schedule and location.

Learning outcomes:

Specific Learning Outcomes:

The objectives of this course are that upon completion the student will be able to:

  1. List the herbicide families, provide examples of commercially available herbicides in that family, state which weeds are controlled.
  2. Understand the modes-of-action of herbicide groups commercially available in Ontario.
  3. Distinguish the injury symptoms and basis of selectivity of the various herbicide modes-of-action.


Lecture Content:

  • Herbicide absorption and translocation
  • Herbicide mode of action
  • Herbicide selectivity
  • Group 1 Herbicides - Aryloxyphenoxypropionates & Cyclohexanediones
  • Group 2 Herbicides – Sulfonylureas, Imidazolinones & Triazolopyrimidines
  • Group 3 Herbicides – Dinitroanilines
  • Group 4 Herbicides – Phenoxies, Benzoic Acids & Carboxylic Acids
  • Group 5 Herbicides – Triazines
  • Group 6 Herbicides – Benzonitriles & Benzothiadiazoles
  • Group 7 Herbicides - Substituted Ureas
  • Group 8 Herbicides - Thiocarbamates
  • Group 9 Herbicides – Organophosphorus
  • Group 10 Herbicides – Organophosphorus
  • Group 13 Herbicides – Isoxalidinones
  • Group 14 Herbicides – Triazolones, Diphenylethers, Dicarboximides and Pyrimidinediones 
  • Group 15 Herbicides – Chloroacetamides  
  • Group 22 Herbicides – Bipyridyliums
  • Group 27 Herbicides - Isoxazoles, Triketones, Pyrazolones, & Benzoylpyrazoles
  • Herbicide Activity – Why do herbicides provide poor weed control?
  • Herbicide Activity – Why do herbicides cause crop injury?
Labs & Seminars:

Seminars will cover:

  • Herbicide Resistance: A “Wicked Problem”
  • Target Site and Non-Target Site Based Resistance
  • Diversity in Target Site Herbicide Resistance
  • Variance in Resistance Among Families within a Herbicide Group
  • 2,4-D – Review of Properties and Uses Auxinic Resistance and the Auxin Signal Transduction Pathway
  • Current State of Herbicides in Herbicide-Resistant Crops
  • State of Knowledge of Group 9 Resistance – Use Patterns and Mechanisms of Resistance
  • Unintended Effects of Shifting Herbicide Strategies to Manage Herbicide Resistant Weeds
  • Technology and Non-Herbicidal Approaches to Managing Herbicide Resistance

Course Assignments and Tests:

Assignment or test Contribution to final mark Learning Outcomes Assessed
Participation in weekly discussions 20% a, b, c
Tests 45% a, b, c
Final exam 35% a, b, c


Final examination:

Please refer to Web Advisor for exam schedule and location.

Course Resources:

Required Texts:

Guide to Weed Control – Publication 75 (2016-2017)

Course Policies:

Grading Policies:
Course Policy on Group Work:
Course Policy regarding use of electronic devices and recording of lectures:

Electronic recording of classes is expressly forbidden without consent of the instructor.  When recordings are permitted they are solely for the use of the authorized student and may not be reproduced, or transmitted to others, without the expressed written consent of the instructor.

Other Course Information:

Additional Course Information

Academic consideration will be made for missed or late assignments/tests/midterms for medical, psychological or compassionate reasons only. No other reasons are eligible for consideration. The use of personal electronic devices such as cell phones, Blackberries, IPods, MP3 players is prohibited during lectures and labs. If a student is unable to write a test on the date in this course outline the student MUST arrange for an alternative time to write the test ahead of time with the instructor. The student must provide a valid excuse for this action to occur. It is strongly recommended that tests and exams are written in pen. If tests are written in pencil they will be marked but will not be re-marked if questions arise later.

University Policies

Academic Consideration

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The Academic Misconduct Policy is detailed in the University Calenders:


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