Department of Pesticide Regulation
Environmental Monitoring and Pest Management
1020 N Street, Room 161
Sacramento, California 95814-5624

Protocol for Development of Methodologies to Assess
Residues of Forestry Herbicides in Plants of Interest to Native Americans


The use of native plant materials is a tradition among Native American tribes in California. A variety of plant materials are collected in diverse locations, including forest lands. Many of these plants are manually processed and/or ingested. The California Indian Basketweaver Association (CIBA) has alerted the California Department of Pesticide Regulation (DPR), the U.S. EPA Office of Pesticide Programs and the U.S. Forest Service of potential exposures to forestry herbicides that may be occurring to Native Americans through the use of plant materials. These unique exposure scenarios are not specifically characterized in the risk assessment of these herbicides. While the U.S. Forest Service has established programs within their national forests to work with tribal representatives to identify and protect designated areas from herbicide spraying, not all Native Americans participate in these programs, and may collect plant materials in unidentified locations. Additionally, there is concern by the Native Americans that the protective measures may not be sufficient.

There are three herbicides that are used in national forest reforestation operations. Glyphosate is a non-selective, postemergent contact herbicide used in reforestation areas. Triclopyr is a systemic herbicide used extensively to control woody weeds and many broad-leaf weeds in reforestation areas. Hexazinone is a contact and residual herbicide also used in reforestation areas. Herbicides can be applied at any time of the year, but predominantly in the spring and fall. Applications of these herbicides are made by commercial applicators under contract with the U.S. Forest Service. While most applications are made by ground application via backpack sprayer, some large acreage projects may utilize aerial application of granular products.

The U.S. Forest Service has requested the assistance of DPR in assessing the residue concentrations of forestry herbicides in plants used by Native Americans. This study is the first of a two-phase project. The first phase will involve the initial development of the appropriate sampling and analytical methodologies, and an estimation of the occurrence of herbicide residues in candidate plants. The second phase will consist of a comprehensive sampling and analytical study of selected plants.


A. Identify sites within the Eldorado, Lassen, Sierra, and Stanislaus National Forests that are scheduled for herbicide treatment for site preparation or vegetation management for fall 1995 and spring 1996.

B. Catalogue sites for plant collection/residue analysis in Eldorado, Lassen, Sierra, and Stanislaus National Forests, where relevant plant species may be exposed to forestry herbicides, both within and outside treatment areas.

C. Develop preliminary sampling and analytical methodologies to measure residues of glyphosate, hexazinone, and triclopyr in candidate plant materials.

D. Conduct pilot sampling to make a preliminary estimate of the occurrence of herbicide residues in candidate plant materials.


This study will be conducted by the Environmental Hazards Assessment Program (EHAP) under the general direction of Kean Goh, Program Supervisor. Key personnel are listed below:

Project Leader: Randy Segawa
Senior Staff Scientist: Heinz Biermann
Field Coordinators: Carissa Ganapathy and Adrian Bradley
Quality Assurance/Lab Liaison: Nancy Miller
Chemist: Cathy Cooper
Contact Person: Madeline Brattesani

Questions concerning this monitoring should be directed to Madeline Brattesani at (916) 324-4100; fax, (916) 324-4088; e-mail,


The following steps will be taken to develop appropriate sampling and analytical methods:

A. Determine Plants of Interest - CIBA and other Native Americans will be consulted to determine possible plant species and plant parts for sampling and analysis.

B. Locate Possible Sampling Areas - Potential treatment areas in Lassen, Stanislaus, Eldorado and Sierra National Forests will be located from discussions with U.S. Forest Service personnel. These treatment areas will be examined for plants of interest, both within and outside the treatment boundaries.

C. Gather Plant Material for Analytical Method Development - Various plants of interest will be gathered in bulk to be used by the laboratory for analytical method development. Ideally, this plant material will come from potential treatment areas. However, the quantity of plants or seasonal growth patterns may make this infeasible. Plant materials from other areas may be substituted.

D. Develop Analytical Methods - The primary laboratory for this study will be the California Department of Food and Agriculture=s Center for Analytical Chemistry. Analytical methods will be developed for a variety of plant species/parts for three chemicals: hexazinone, glyphosate and triclopyr. The method detection limit and reporting limit will be determined for as many different species and parts as possible, given funding constraints. The method detection limits will be determined using U.S. EPA procedures, and as described in EHAP standard operating procedure QAQC001.00. In addition to providing an estimate of the detection limits, these analyses will give preliminary information on the precision, accuracy, interferences and costs that will be associated with each method.

Complete validation of the laboratory methods (as described in EHAP standard operating procedure QAQC001.00) will not be conducted for this study. The pilot sampling that will be conducted in phase 1 will only determine the presence or absence of herbicides in plant samples. Therefore, a quantitative determination of residue levels is not necessary. By postponing method validation, a greater number of samples can be collected and analyzed for the pilot study. In addition, only plants selected for further study will need to be validated. Funds will not be expended to validate methods that may not be used.

It is expected that all plants will be analyzed for total residue only (combined dislodgeable and internal residue). Separate dislodgeable analyses are not expected to be conducted for several reasons. 1) The greatest concern for many Native Americans is the presence or absence of pesticides. Whether the pesticide is present as dislodgeable or internal residue is of secondary importance. 2) Analysis for total residue only will reduce costs and/or increase the number of samples. 3) There will be no quantitative information available regarding the physical handling of plant material by Native Americans. Since dislodgeable concentrations are normally expressed on an area basis (e.g., milligrams per square meter), the data will have little meaning. 4) Measuring the surface area of plant samples could be tedious, inaccurate and costly. For example, there are no reliable methods to measure the surface area of grasses, acorns, or willows, especially after a dislodgeable analysis. 5) A dislodgeable analysis should be done before the plant material starts to decay. The analysis is typically done within 24 hours of sampling even when samples are kept refrigerated. Logistical problems of getting samples from the forests to the laboratory will make this very difficult. Dislodgeable analyses will only be done if the advantages outweigh these disadvantages.

E. Develop Sample Collection Procedures - Appropriate field sampling procedures will be developed for each plant species to be analyzed. Most of the plants of interest contain insufficient mass for a single sample within an individual plant. Therefore, a single sample will consist of composite material from several plants. The development of sampling procedures will include a list of appropriate tools and materials, methods for obtaining representative samples, number of plants comprising a single sample, size of area to be represented by a single sample, handling the samples, appropriate containers to use, cleaning procedures for sampling tools, methods of storage (storage temperature), and chains of custody.


Following method development, pilot sampling will be conducted. The pilot sampling will consist of a survey for the occurrence of herbicide residues. No quantitative assessment of herbicide concentrations will be conducted in this survey. The specific objective of the survey is to make a preliminary estimate of the occurrence of herbicide residues in plants of interest collected from treated and untreated areas (as identified in IV.B). Sampling and analysis will be conducted for each plant for which an analytical method is developed, and can be found within or near treatment areas. Results of the survey will be used to help identify possible plants, areas and herbicides for further study in phase 2.

A. Plants for Survey - The survey will attempt to sample as many plants of interest as possible given time and resource constraints. The following plant materials have been collected in sufficient quantity to develop analytical methods:

Anaphalis margaritaceae (pearly everlasting-foliage and flowers)
Arctostaphylos spp. (manzanita-berries)
Ceanothus cuneatus (buck brush-shoots)
Ceanothus integerrimus (deer brush-shoots)
Clorogalum pomeridianum (soaproot-bulb)
Cornus spp. (dogwood-stems)
Ericamera arborescence (golden fleece-foliage)
Muhlenbergia rigens (deergrass-stalks)
Prunus emarginata (bitter cherry-shoots)
Pteridium aquilinum (bracken fern-rhizome)
Quercus spp. (Oak-acorns)
Salix spp. (willow-shoots)
Sambucus spp. (elderberry-berries)

Development of methods for all of these plants will be attempted. However, analytical difficulty or time constraints may preclude this. Some commonly used plants such as red bud and wild onion did not occur within proposed treatment areas, at least at the time treatment areas were examined. Additional plants may be studied if they occur within treatment areas, can be obtained in sufficient quantity, and methods developed prior to the survey.

B. Types of Applications - For the purposes of this study, herbicide applications have been classified by active ingredient and method of application. Currently, the U.S. Forest Service uses five different products each containing one of three active ingredients. These herbicides can be applied by three methods: directed or spot treatment by ground, broadcast by ground, or broadcast by air. The following types of applications are currently used:

hexazinone/air: Pronone/broadcast/air
hexazinone/ground: Pronone/broadcast/ground
glyphosate: Accord/directed/ground
triclopyr: Garlon/directed/ground

Plant samples will be collected from each of the four major types of treatments, as detailed below:

Lassen - hexazinone/ground
Eldorado - triclopyr
Stanislaus (Paper) - hexazinone/air
Stanislaus (Hamm-Hasloe) - hexazinone/ground, glyphosate, triclopyr
Stanislaus (Groveland Conifer Release II) - glyphosate
Sierra - hexazinone/ground, glyphosate

For the survey, occurrence of hexazinone in plant materials is of primary interest. Pronone is a granular herbicide and requires translocation to be detected in plants. A plant treated with Pronone may or may not contain herbicide residue. The other herbicides are liquids sprayed directly on plants and are certain to contain herbicide residues. Occurrence of all herbicides in untreated areas is also of interest.

C. Treatment/Sampling Areas - The characteristics of individual treatment areas vary greatly. The size of the individual treatment areas varies from one to hundreds of acres. The elevation varies from 3000 to 7000 feet. The slope varies from 0 to 100% or more. The treatment areas can either be for Asite preparation@ (prior to planting) or Arelease@ (after planting). The types and abundance of plants of interest within the treatment areas varies greatly. The treatment areas examined to date contain none to five plant types in sufficient abundance for sample analysis. Many of the treatment areas contain protected areas, usually streams or drainages, which are left untreated. In addition, some plants are intentionally avoided. The survey will attempt to sample as many plant types as possible in both treated and untreated areas.

D. Sampling Schedule/Plan - The dates of sample collection will be dictated by treatment schedules and plant growth. The first treatments occurred in late November 1995 and will continue through spring 1996. Samples will be collected after the herbicides have started killing target plants. Sampling will continue until seasonal growth is sufficient to allow sampling for each plant type. Samples of surviving and avoided plants will be collected. Those plants treated directly and/or showing overt toxicity will be known to contain residues and will not be sampled in phase 1. The proposed treatment and sampling schedule is shown in Figure 1. However, this schedule is subject to change. The total number of samples that will be collected is difficult to estimate because the number of laboratory methods that will be ready, the number of plant types that will be available in treatment areas and plant abundance are unknown. The current estimate is that 100 - 200 samples will be collected.


Since no quantitative analyses will be conducted for this study, significant changes in EHAP standard operating procedures will be implemented. Method development will consist only of method detection limit and reporting limit determinations. No method validation or storage stability analyses will be conducted in phase 1. Continuing quality control will include solvent blank samples and matrix spike samples. One blank sample and one spike sample will be analyzed with each set of samples.


No statistical analysis of the data will be conducted. The pilot sampling data will be used qualitatively to assist in the selection of the plants, areas and herbicides for further study. Individual sample results will be expressed as positive/negative or a range of concentrations.

Very few if any definitive conclusions will be made regarding the pilot sampling data. Even if no herbicides are detected in any of the samples, we will not be able to conclude that all plants of the species sampled will have no detectable herbicide residues. Conversely, even if all samples contain herbicides, we will not be able to conclude that all plants of the species sampled will contain herbicides. Most likely some of the samples will be positive and some will be negative and we will conclude that herbicide residues will occur in some plants of interest under some circumstances. Phase 2 will attempt to identify the circumstances or variables that effect herbicide residues in plants of interest.


This timetable is significantly different from the one first proposed because of delays in the contract approval and changes in the pilot sampling. The contract with the U.S. Forest Service requires a report to be completed by May 1996. However, sampling is scheduled to continue until September 1996. If necessary, an interim report will be provided to the U.S. Forest Service in May 1996 to fulfill the terms of the contract.

Site Identification: August 1995 - January 1996

Method Development: September 1995 - March 1996

Pilot Sampling and Analysis: March - September 1996

Report Preparation: September - December 1996