N A V I G A T I O N  HOME  LESSONS       Animations       Quiz       Glossary       My Progress       Login request       Lost Password       Contact Instructor       FAQ  USING LESSONS  HISTORY OF PROJECT  ACKNOWLEDGEMENTS  LICENSES  DOWNLOADS  REVIEW  PROFESSIONAL SOCIETIES

Appearance of Herbicide Resistance in a Weed Population: Introduction J. Anita Dille Department of Agronomy at Kansas State University, USA Deana Namuth Department of Agronomy and Horticulture at University of Nebraska-Lincoln, USA Lesson Navigation Tips: - Click on 'Animations' button found to the left in order to view the animation which supplements this lesson. You can also click on the animation icon within the text. - Click once on figures to see enlarged versions. - Click once on words in rust color to bring up their definitions. Overview: Through the repeated imposition of the same herbicide, susceptible (S)- biotypes of a weed species are controlled and herbicide resistant (R)-biotypes of the same weed species are left behind to reproduce and return seed with the resistance characteristic back into the soil. This lesson will highlight the population dynamics of a mixed weed population (S- and R-biotypes) and compare and contrast the rate at which herbicide resistance appears in a weed population under a diversity of selection pressures. Objectives: At the completion of this lesson, students will: 1. Understand the differences between susceptible, tolerant, and resistant weed populations. 2. Describe diagrammatically and mathematically, the dynamics of an annual weed species population composed of S- and R-biotypes. 3. Describe herbicide characteristics, aspects of weed species biology, and management practices that alter intensity of selection pressure and impact the rate at which herbicide resistance appears in a weed population. 4. Devise a weed management plan with a diversity of selection pressures to reduce the rate at which herbicide resistance appears. 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). 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. A contribution of Kansas State University and the University of Nebraska Cooperative Extension. Journal series No. 1025