Auxin and Auxinic Herbicide Mechanism(s) of Action - Part 1 - Introduction - Overview and Objectives


The selective control of broadleaf weeds in cereal grain crops by auxinic herbicides has made this group one of the most widespread and important herbicide families in use. These herbicides were the first organic herbicides developed that were selective or able to kill one group of plants, but not another (i.e. kill broadleaf, but not grass plants). This lesson will introduce the major features of these herbicides, discuss their major uses and describe the symptoms of the injury they cause as well as introduce how they kill sensitive plants.


At the completion of this lesson, students will be able to:

  1. Identify the four major classes of auxinic herbicides and their characteristics.
  2. Understand the selective nature of this group of herbicides.
  3. Describe how auxinic herbicides mimic the natural plant hormone, auxin and act in plants.
  4. Recognize the major damage symptoms caused by auxinic herbicides in broadleaf and grass plants.
Peer Reviewed Web Lesson JNRLSE Approved 2004

Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number 00-34416-10368 administered by Cornell University and the American Distance Education Consortium (ADEC) and the New Mexico State University Agric. Exp. Stn. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. This manuscript has been assigned Journal Series No. 03-12, College of Agricultural Sciences and Natural Resources, University of Nebraska.