Mesquite Treatment and Rangeland Restoration

One of the goals of the grassland restoration project is to return the segment of the San Simon riverbed at the Painted Pony Resort to open grassland, creating a seed reservoir, and this means removing mesquite.  The riverbed was over run with mesquite as a result of unmanaged cattle grazing.  Cattle are a major dispersal agent in the spread of mesquite, eating and passing seeds back onto the landscape where they germinate.  Originally confined to riparian areas, mesquite has spread across the landscape in modern times.  But it is not all bad, mesquite provide forage for cattle and other native browsers, habitat for nesting birds, and most importantly they fix nitrogen in addition to holding the soil.  Mesquite can be stubborn to remove since they produce deep tap roots and mechanically removed mesquite come back quickly requiring further treatment.  A backhoe or other device that will pull the taproot out is required to completely remove the plant and prevent regrowth.  Alternatively, herbicide treatment may be used after initial removal of the above ground portions of the plant.  But tests by others with a number of different herbicides show variable results with both application timing and herbicide compound being important variables.  Because of the variable results with different herbicides a 2 prong approach was chosen for herbicide treatment.  Glyphosate (the active chemical compound found in Roundup) is available off label at 40% concentration.   This is diluted to a final concentration of 2% (found in commercially available formulations) and combined with 2,4-D at a final concentration of 0.2%.  2,4-D is a plant hormone analogue while Glyphosate interrupts amino acid synthesis.  Once absorbed both herbicides work through different mechanisms interrupting plant growth and killing the reoccurring mesquite.  Below are photographs of a mechanically removed mesquite in the riverbed treated with this combination of herbicides.  Although effective some regrowth is noted requiring a second application to finish off the mesquite.

This combination of mechanical removal followed by herbicide treatment is returning the riverbed to an open grassland while maintaining a few large single stemmed mesquites for habitat and leaving mesquite along the margins and on the uplands to provide cover, soil stabilization, and nitrogen fixation this approach shows what may be accomplished with a minimal investment.  

Untreated, 2 weeks after mechanical removal

96 hrs post herbicide treatment

10 days post herbicide treatment, residual new growth will require a second treatment


  1. We have quite a crop of pig weed coming up where we grubbed out a mesquite. We thought about Round Up but don't know the residual effects so we will use the old shovel. Bugs are terrible now so we need either some cold nights to kill the bugs or a really windy day to get this done.

  2. Yes, I have pig weed again this year. It is the material I used to create the test topsoil barriers which are shown in a post below. I noticed an increase in small flying bugs this year and even slapped a mosquito the other day.

  3. I should also point out that I have seen an increase in ground birds since starting this project. Quail (both Gambel's and Scaled) as well as large flocks of doves are now present in the section of fenced riverbed on the estate.

  4. Our quail population is up this year but its probably just the ebb and flow of the rain and the plants the momma's need for multiple egg laying. We need some birds here that eat gnats!

  5. I agree. After yesterdays rain I was in some lower areas with no breeze and could hear the gnats buzzing around.