Controlling Medusahead with Intensive Grazing

The Issue

Medusahead is an aggressive and invasive non-native annual grass causing severe undesirable effects on western rangelands. Medusahead grows on more than a million acres of grassland, oak woodland and chaparral shrubland in California. The presence of medusahead can reduce the land’s livestock carrying capacity by as much as 75 percent. Medusahead also impacts ecosystems by reducing plant diversity, the productivity of desirable plants, and wildlife habitat. Medusahead control has been explored since the 1950s, but with limited success. Burning is an effective method, but it is not widely used because of air quality and liability issues. Herbicides are not practical in rough terrain and selective herbicides targeting medusahead are not available.

What Has ANR Done?

A team of UC Davis professors, UC Cooperative Extension specialists and UCCE advisors researched the use of intensive grazing and mowing to control medusahead.

An initial project, conducted in western Yolo County, studied three intensive grazing schedules based on the phenology of medusahead and other rangeland plants. The scientists found that high-density, short duration grazing in late-spring achieved over 95 percent control of medusahead and increased plant diversity by encouraging the growth of many native plant species. High-density grazing creates intense competition between animals, compelling them to graze more uniformily and less selectively. This is necessary since medusahead has low palatability. Grazing medusahead plants immediately after elongation of internodes and before they develop their highly unpalatable seadheads was critical to achieve control.

Excellent control was obtained with very high-density and short-duration grazing, but these levels are difficult for many ranchers to duplicate. Additional funding expands the research to ranches from Tehama to San Luis Obispo counties and will examine the effect of lower animal densities and longer grazing periods on medusahead control.

The Payoff

Changing attitudes and strategies in controlling medusahead

This research demonstrates that properly managed and timed grazing can successfully control medusahead and increase plant species diversity in California rangelands. These results contribute to the growing body of knowledge, scientific and anecdotal, that livestock grazing can have positive environmental impacts if properly managed. As a direct result of this project, the practice of using livestock for the purpose of controlling medusahead and other noxious weeds is being tested and adopted by progressive rangeland managers and ranchers throughout California. Weed control through grazing management is potentially less damaging to the environment than alternative weed control methods, such as herbicides, mowing and burning, and makes use of a resource readily available on California rangeland — the livestock themselves.


Supporting Unit:

Solano County, Department of Plant Sciences, UC IPM

Morgan Doran, Livestock & Natural Resources Advisor, Solano County,, (707)784-1326