To Our Ojai Community:

Thank you for your patience and understanding as we recover from the damage from the Thomas Fire on our trails. In the coming months trails will likely open and close depending on rain and changing trail conditions. Click here for current information and trail notifications »

Comparative Analysis of Glyphosate Applications in the Ventura River Watershed

OVLC Arundo Removal Project and Watershed-Wide Glyphosate Applications

The Ojai Valley Land Conservancy’s Arundo donax removal project is part of a regional, multi-agency, effort to address one of the most important threats to riparian resources in the Ventura River Watershed. Left unaddressed Arundo donax will cause irreparable harm to riparian habitats and the fish and wildlife that depend on these habitats, as well as create fire, flood, and continuing drought hazards. After thoroughly researching methodological options, it has been determined that the removal of biomass in combination with direct application of glyphosate herbicide is the method that will be most effective while having the least environmental impact to the project areas. Alternative methods have been assessed, but none have shown to be effective at a large scale and the OVLC is limited in methodological options by regulatory agencies that must grant permits for Arundo removal. For example, excavation of the plant along waterways is prohibited due to the impacts it would have on streams and bank stability. Approximately 200 acres have already been removed by various agencies watershed-wide since 2005, leading to recovery of native habitats and riparian functions, as well as increases in natural biodiversity. During this time there have been no documented incidents of environmental degradation or health impacts from Arundo removal projects. This paper provides some context to the use of herbicide for natural resource management as it relates to overall herbicide use in the Ojai Valley.

It is an important point of differentiation that this project has a limited duration based on specific project sites and does not constitute a management practice that would utilize significant volumes of herbicide beyond the project timeline. In fact, use of herbicide decreases rapidly following the first treatments as the Arundo dies back and less requires treatment. The current OVLC Arundo removal project is being implemented on 23 acres along the lower five miles of San Antonio Creek and is expected to be mostly complete by 2020.

Data on pesticide use in the Ventura River Watershed is available from databases maintained by the California Department of Pesticide Regulation. Licensed pesticide applicators, such as those working on behalf of the OVLC, must submit use data for inclusion in the database. The state’s database is behind in posting updated information and only includes data through 2016. The 2017 and 2018 data have not yet been posted. The OVLC does receive copies of the reports filed by our contractors. The data for the OVLC’s current Arundo removal project is included in this summary and represents a time period beginning in the Fall of 2016 when the project began, and continuing through May 2018. It is, therefore, not yet possible to directly determine how much of the total herbicide used in the Ventura River Watershed was applied by the OVLC contractors for these years. Therefore, this report compares the annual use of herbicide by the OVLC for 2016, 2017, and 2018, with the average annual use in the period between 2012 and 2016, (five years) as the most recent comparative years.

This report focuses only on the use of Roundup-branded products and other glyphosate products registered under different names and does not contain the myriad of other substances used throughout the area. There are a variety of mixtures that are marketed for varying applications using the “Roundup” brand, and they are not all the same. Some of these include Original Roundup, Roundup Pro Concentrate, Roundup Pro Max, Roundup Quickpro, Roundup Weathermax, Roundup Brush Killer, Roundup Weed and Grass Killer, and Roundup Custom. There are many more still.

For OVLC Arundo removal only Roundup Custom is used. According to the Material Safety Data Sheet (MSDS), Roundup Custom contains Isopropylamine salt of glyphosate (53.8% by weight) and water (46.2% by weight). This version of Roundup was chosen because it does not contain a surfactant or other materials unknown to the user that may be more toxic than glyphosate. Very low volumes of crop oil and marking dye are also used, which are considered to have low toxicity. The low volume and careful application techniques prevent any significant environmental exposures to these items.

Total Roundup Applications in the Ventura River Watershed

To determine comparative usage of roundup-branded products and all glyphosate products, data queries were made of the California Pesticide Information Portal (CALPIP) for the past five complete years of data (2012-2016). The geographic regions searched to represent the Ventura River Watershed include the zip code zones that overlay the watershed (93023, 93022, 93001). Some of this region lies outside of the Ventura River Watershed. Data on OVLC usage of Roundup Custom comes from the OVLC’s contractors. The OVLC data is reported as gallons of total product used. The state CalPIP database reports volumes in lbs of active ingredient. For comparative purposes, the CalPiP data has been converted to gallons of product by dividing the pounds of active ingredient by a factor of 5.4, which is the weight of active ingredient that are present in 1 gallon of Roundup Custom (Roundup Custom Label).

Total Glyphosate/Roundup Used

The CalPIP database was searched for all Roundup branded materials and all glyphosate products for each year starting in 2012, and continuing through 2016. The five-year average annual use of Roundup-branded products is 994 gallons. When all glyphosate products are considered the average annual application is over 3,600 gallons. Figure 1 shows OVLC usage in comparison with the annual average usage of all glyphosate and Roundup-branded products.

Figure 1 – Comparative Use of Glyphosate Products

The glyphosate present in Roundup Custom has a relatively short lifespan once applied so periodic applications do not to cause accumulation of the substance in the environment. From Jeff Schuette 1998, Environmental Fate of Glyphosate, Environmental Monitoring & Pest Management Department of Pesticide Regulation Sacramento, CA:

  • Glyphosate’s primary route of decomposition in the environment is through microbial degradation in soil (Franz et al. 1997). The herbicide is inactivated and biodegraded by soil microbes at rates of degradation related to microbial activity in the soil and factors that affect this activity.
  • Glyphosate does not volatilize so it does not degrade through the air or migrate in gaseous form.
  • A study on the effects of glyphosate on microbial biomass found glyphosate generally had no significant effect on the numbers of bacteria, fungi, or actinomycetes in forest soil and overlying forest litter.
  • Glyphosate’s low octanol/water coefficient and low fat (lipids) solubility indicate that it has a low tendency to bio-accumulate.
  • The average rate of dissipation of foliar residues was 2 days for 50% dissipation and less than 16 days for 90% dissipation.

The OVLC Arundo removal project uses periodic treatments so materials previously applied on the same site will have decomposed prior to additional applications. Thus, no accumulation of the product is likely.

Top Uses

Cumulatively the OVLC’s Arundo removal project makes up a small fraction of the annual use of Roundup-branded products and total glyphosate products. The data collected by the California Department of Pesticide regulation breaks out the commercial use of glyphosate products by what crop is present on the area of application or what land use is designated for the application area. The vast majority of product use is concentrated among orchard crop areas growing avocados, lemons, oranges, and tangerines.  In 2016, the OVLC Arundo Project contributed 0.6% of total glyphosate products used in the study area (by weight).

Use of glyphosate for Arundo removal is a disperse use geographically. The OVLC project covers 23 acres of Arundo.  The chart to the right shows the volume of glyphosate per acre on the project. This shows an emerging trend of significant decline with each year.


As the data indicate, use of Roundup-branded products and total glyphosate products are highly clustered in agricultural areas growing four primary crops. The consistency of the annual use illustrates a use best described as a land management program. In contrast, use of these products for natural resource management is episodic and constitutes only a fraction of total use in the study area.

As stated in this report, these data represent the applications of total glyphosate and “Roundup” branded products that are reported to the California Department of Pesticide Regulation. These data represent uses by commercial operators that are licensed for the commercial application of these products. These data do not include the applications of any glyphosate products applied by homeowners in residential areas.

More facts about Arundo Removal »