Grazing Strategies to Control Medusahead in California

2009 Annual Report for SW06-038

Project Type: Research and Education
Funds awarded in 2006: $138,539.00
Projected End Date: 12/31/2010
Region: Western
State: California
Principal Investigator:

Grazing Strategies to Control Medusahead in California


We studied precision grazing to control medusahead. High-density short-duration grazing when medusahead is at the internode elongation and boot stages dramatically reduces medusahead infestation. Susceptible phenological stages are predictable but vary over regions. Low-moisture supplement placed in medusahead patches increases grazing intensity, but the effect is localized. Results and approaches were disseminated in several regional and national meetings, and by direct communication with producers. Based on recommendations from stakeholders we also tested mowing and non-selective herbicides as additional control tools that can be used with a precision approach. The objectives for this last year of the project were to complete measurements in experiments that were delayed by lack of rain in 2007. A detailed final report will be submitted in 2010.

Objectives/Performance Targets

Project goals

Objective 1. Design a simple and cost-effective “precision” grazing method to control medusahead (Mh), and incorporate it into the grazing systems of California annual rangelands.

Objective 2. Study the effects of spatial distribution of attractants such as supplement on spatial distribution of grazing pressure, and use new knowledge to implement supplementation methods to reduce Mh infestations.

Objective 3. Develop and implement a site-specific and simple system to identify and forecast the period of Mh’s greatest susceptibility to mowing and grazing, and establish a warning system for ranchers to accurately time grazing.

Objective 4. Disseminate, demonstrate, and document results in extension fact sheets, field visits, and newsletters by Farm Advisors.

Goals for final year

April-May 2009: Sample vegetation at the Owens ranch and Putah Creek Dorsets ranch. Exact timing will depend on rainfall pattern.
June 2009: Prepare and submit forage samples to have fiber and CP determined.
June-July 2009: Collect seed production samples. Determine botanical composition of herbage samples and enter data.
Aug-Nov 2009: Incorporate 2008 data into phenology models. Gather weather data for sites that were not sampled.
Dec 2009: Remove fences and exclosures from ranchers’ fields.
Jan-Mar 2010: Analyze data from 2008-9 grazing season for Owens and Putah Creek sites. Complete and distribute PhD Dissertation.
April-May 2010: Prepare final report and visit participating ranches to deliver final results. Submit manuscripts to peer-reviewed journals.


Objective 1. Grazing medusahead between internode elongation and anthesis with stocking densities of about 5 AU/ha during two weeks reduced cover of this weed by more than 60% in the following season. System was implemented in four ranches.

Objective 2. Supplementation with low moisture blocks increases local grazing pressure in medusahead patches up to 50 m from the supplement. Increased pressure reduced medusahead cover, although less effectively than precision grazing. Supplementation schemes were implemented in four ranches.

Objective 3. We developed models to forecast susceptible phenological stages. Models need to incorporate the last year of data and they need to be incorporated into the Weed and Rangeland websites.

Objective 4. We produced two Agriculture and Natural Resources informational sheets, contributed to several popular press articles, demonstrated the project during four field days, presented results and grazing techniques in 5 producers’ meetings, two State meetings, two international meetings, three meeting to UC-ANR scientists and extensionists, and three meetings for high school students and their families. Several manuscripts for peer-reviewed journals have been prepared. Nine Farm advisors and Extension Specialists participated actively in the project and disseminate the information directly to their clienteles. Personnel from the NRCS, Audubon California, and State Parks participated in field days and received information about the results of this research.

Impacts and Contributions/Outcomes

This project resulted in the demonstration of targeted grazing, precise application of herbicides and use of grazing attractants to control medusahead. New precise knowledge about the biology and phenology of this annual weed was generated towards effective control methods.

Costs and benefits of medusahead control were analyzed and compared for several methods. Results indicate that all methods are cost effective.

Ranchers, agency personnel, and the general public have been made aware of the problems created by exotic weed invasions. Tools to monitor and control medusahead are disseminated in fact sheets, magazine articles, peer-reviewed journal articles, and web pages.


Jim Yeager
34791 Creeks Edge Road
Davis, CA 95616
Office Phone: 5307562423