USDA Forest Service 

Pacific Southwest Region

Salmon River 

Knapweed Project 

Environmental Assessment 

Salmon River Ranger District

Klamath National Forest

June 2000
ii SALMON RIVER Knapweed Environmental Assessment 

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of 

race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. 

(Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for 

communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at 

(202) 720-2600 (voice and TDD). 

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 

1400 Independence Avenue, SW, Washington, D.C. 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an 

equal opportunity provider and employer. 
SALMON RIVER Knapweed Environmental Assessment iii

Table of Contents 

Page

Chapter 1 Purpose and Need for Action

Purpose and Need For Action...............................................................................1 

Proposed Action – Integrated Pest Management .................................................3 

Decision To Be Made ...........................................................................................7 

Public Scoping and Issues ....................................................................................7

Chapter 2 Alternatives

Alternatives Considered in Detail .........................................................................9 

Standard Operating Procedures and Mitigation Measures ...................................9 

Alternative 1 – The Proposed Action ..................................................................12 

Alternative 2 – Community Based Alternative ....................................................12 

Alternative 3 – Modified Proposed Action ..........................................................13 

Alternative 4 – No Action Alternative...................................................................15 

Comparison of Alternatives ................................................................................16 

Alternatives Considered but not in Detail ...........................................................16 

Chapter 3 Environmental Consequences

Issue 1 – Human Health and Safety ..................................................................17 

Hazard Analysis ...............................................................................................18 

Risk Analysis ...................................................................................................20 

Characteristics of Proposed Herbicides in Alternatives 1 and 3 .......................22 

Effects of Alternatives.......................................................................................24 

Effects Common to Alternatives 1 and 3 ..........................................................26 

Issue 2 – Water Quality and Aquatic Species ....................................................30 

Water Quality Effects .......................................................................................30 

Characteristics of Proposed Herbicides in Alternatives 1 and 3 ...................31 

Water Quality Control Board Basin Plan .......................................................36 

Effects to Aquatic Species ...............................................................................37 

Issue 3 – Effects to Non-Target Species ............................................................43 

Botanical Analysis..........................................................................................43 

Wildlife Analysis.............................................................................................43 

Issue 4 – Effects to Federally Listed, Proposed and 

Forest Service Sensitive Species ..................................................................55 

Issue 5 – Effects to Local Community Well-Being and Quality of Life ................57 

Issue 6 – Adverse Effects from the Use of 2,4-D................................................58 

Issue 7 – Chemical Herbicides Should Be Used as a Last Resort......................59 

Achievement of Purpose and Need for Action ....................................................60 
iv SALMON RIVER Knapweed Environmental Assessment 

Table of Contents 

(continued) 

Page

Chapter 4 List of Preparers; Agencies and Persons Consulted........ 62

Appendices

Appendix A – Human Health and Safety Risk Assessment 

Appendix B – Best Management Practices 

Appendix C – Spill Contingency Plan 

Appendix D – Water Quality Monitoring Plan 

Appendix E – Analysis of Potential Runoff Scenario 

Appendix F – References Cited 
SALMON RIVER Knapweed Environmental Assessment 1 

Chapter 1

Purpose and Need for Action 

The Klamath National Forest Land and Resource Management (LRMP) provides management 

direction, goals, and objectives for meeting desired conditions in the project area. The LRMP (pg. 4-

6) requires management for viable, healthy plant populations of native and desirable non-native plant 

species. The purpose and need for action is to move the existing condition of the project area from 

that of a spreading infestation of noxious weeds to a desired condition of a healthy, biologically 

diverse ecosystem. 

Spotted knapweed, Centaurea maculosa, and diffuse knapweed, Centaurea diffusa, have been 

identified as introduced noxious weeds in the Salmon River drainage. Knapweeds are considered to 

be a public nuisance by the State of California. They are classified as "Class A" pests; aggressive 

competitors that are targeted for priority eradication before their numbers are too great to successfully 

eliminate. Because knapweed is considered a public nuisance and an “A” rated pest, the acceptable 

tolerance for it to occur is zero. This means the objective for treatment is 100 percent elimination. 

Knapweed has tremendous potential to rapidly infest and degrade large areas, as has been 

documented in Idaho and Montana (Sheley and Petroff, 1999; USDI, 1996) and other areas in the 

inter-mountain west where millions of acres have been converted to these noxious weeds. 

Knapweed, an introduced non-native perennial plant species from the European continent does not 

have natural predators in this area. It can out-compete native vegetation and is adapted to a variety of 

conditions. When knapweed takes over a site and spreads, it replaces native vegetation and biological 

diversity is lost. Knapweeds produce a chemical that inhibits growth of native surrounding 

vegetation. Soil stability is reduced as knapweed has a narrow tap-root with low soil holding 

capacity. Knapweed has very low value as a forage species or habitat component for wildlife. 

Knapweed thrives on disturbance, which is why there is concern along the river bar and floodplain as 

well as in the upland areas of the Salmon River watershed. Historic and recent fires and flooding 

have created disturbance regimes conducive to the spread of knapweed. The fact that the major 

infestations occur along the floodplain is cause for particular concern as the high flows have the 

potential to spread seed and plant material anywhere down stream in the watershed and beyond. The 

fact that the upland sites are in close proximity to the Specimen Fire site which burned in 1994, and 

to the Marble Mountain Wilderness Area, also increases the urgency of the need for prompt treatment 

as the potential for spread in these areas is high and treatment options are limited due to accessibility 

and terrain. 

The California Department of Food and Agriculture (CDFA) is the lead agency in the State for 

preventing noxious exotic plants from spreading or becoming established in California through early 

detection and immediate control or eradication efforts (CDFA Food and Agricultural Code of 

California, Section 403 and Title 3, California Code of Regulations, Sections 4500). The program is 

conducted cooperatively between CDFA and County Agricultural Commissioners. The Code (Div. 4, 

Chapter 1, Section 5004) defines noxious weeds as “any species of plant which is, or is liable to be, 

detrimental or destructive and difficult to control or eradicate” and rates plant pests into categories 

(USDA, 1996). Section 5401 states “Any premises, plants, conveyances or things which are infected 
2 SALMON RIVER Knapweed Environmental Assessment 

with any pest or premises where any pest is found, are a public nuisance, and shall be prosecuted as 

such in all actions and proceedings. All remedies which are given by law for the prevention and 

abatement of such a nuisance apply to such a public nuisance.” 

When noxious weed infestations extend onto National Forest Lands, the development of a 

cooperative agreement allows the State and/or County to extend eradication and/or control activities 

onto National Forest lands, provided all Federal codes and laws are met (MOU, 1995). 

Specific management direction for the control and eradication of noxious weeds is contained in the 

Forest Service Manual (FSM), Carlson-Foley Act of 1968, and the Federal Noxious Weed Act of 

1974. The Carlson-Foley Act of 1968 directs agency heads to enter upon lands under their 

jurisdiction with noxious plants and destroy noxious plants growing on such land. FSM 2080 states: 

“The Federal Noxious Weed Act of 1974, as amended (7 U.S.C. 2801, et seq.), requires cooperation 

with State, local, and other Federal agencies in the application and enforcement of all laws and 

regulations relating to the management and control of noxious weeds.” Forest Service regulations at 

36 Code of Federal Regulations (CFR) 222.8 acknowledges the Agency’s obligation to work 

cooperatively in identifying noxious weed problems and developing control programs in areas where 

NFS lands are located. 

When assigning management priorities for the prevention and control measures, the Forest Service is 

to utilize Noxious Weed Classifications Systems developed at the State or County level to provide a 

coordinated approach. This is the system that classifies spotted and diffuse knapweeds as Class A 

pests. The policy of the State of California for spotted and diffuse knapweeds is an eradication 

program. The spotted knapweed infestation on the Salmon River is one of the largest in the State, 

and the largest in Siskiyou County. 

The objective of this proposed action is to eradicate known populations of the 

species and prevent the introduction and establishment of the species in other 

areas of the Forest and adjacent lands. 

There is much speculation as to the source of the initial introduction of spotted knapweed in the 

Salmon River corridor. More than likely it was brought in on vehicles or equipment to the Kelly 

Gulch river bar and spread from there by high water, vehicles, equipment, animals, and people to 

other locations during the last 10 to 15 years. In 1997, the increasing number of knapweed plants 

discovered in the area became recognized as a serious problem. 

Starting in 1997, intensive mechanical treatment was initiated to control knapweed in the Salmon 

River area through a cooperative effort with local community volunteers. Over 300,000 plants (both 

adults and juveniles) have been pulled and removed. Over 300 gross2 acres have been treated, 

inventoried, and/or monitored. The hand pulling effort has been successful in reducing the number of 

mature plants and in areas of limited plant numbers (25 or less); however, in areas of high plant 

densities and under challenging conditions (rocky, dry, steep, inaccessible and heavily infested), 

success has been limited to reductions in numbers of plants and a holding action of preventing 

flowering and seed set. All sites have experienced increases in seedlings, juvenile plants, and 

germination enhanced by disturbance. 

 

2

 Gross acres are all inclusive (inventoried and treated). 
SALMON RIVER Knapweed Environmental Assessment 3

Research indicates that the most effective means of controlling knapweed is through the judicious use 

of herbicides at the appropriate stage of plant development. Studies indicate that herbicides were 

greater than 90% effective in controlling plants, while hand-pulling was 56% effective (reference 

“Cost and Efficacy of Spotted Knapweed Management with Integrated Methods” Brown, Duncan, 

Halstvedt, 1999). In all cases, continued monitoring and follow-up treatment is important. 

Knapweed seed can maintain viability for as long as nine years. Exhausting the current seed bank 

may take several years. 

It is important to act quickly and aggressively in the short term while the population is still relatively 

manageable and successful treatment is still feasible. Not taking action now may preclude any 

opportunities to effectively eradicate or control this pest.

Proposed Action - Integrated Pest Management 

The Klamath National Forest, Salmon River Ranger District proposes to implement an integrated pest 

management program to eradicate infestations of spotted knapweed, Centaurea maculosa and diffuse 

knapweed, Centaurea diffusa within the Salmon River drainage. The methods include manual and 

chemical treatments. The project area and areas of known infestations of knapweed are shown on the 

attached map. Due to diverse geographical and environmental conditions within the project area, the 

proposed action will provide a range of weed eradication methods appropriate for various site 

conditions. 

The major infestations of spotted knapweed occur in riparian areas along the North Fork of the 

Salmon River and in upland areas of Kelly Gulch, Little North Fork, and Specimen Creek (refer to the 

Vicinity Map and Project Area Map enclosed). Currently spotted knapweed has been located on 130 

individual sites. Diffuse knapweed has been located on only four sites (one of which contains both 

species of knapweed) within the project area at this time. Over 300 acres of potential habitat have 

been inventoried for knapweed; approximately 150 acres of which are mapped sites containing 

knapweed. Of these treatment acres, individual plants and the immediate vicinity would be treated, 

rather than entire plant communities. The total estimated treatment area is approximately 15 acres. 

The proposed action would allow for treatment of up to 30 acres as needed based on on-going 

inventory. Actual treatment acres proposed are estimated to be 10% of the total infestation acreage 

figure (personal communication, B. Krebs, CDFA). 

The United States Department of Agriculture, Forest Service (USFS) proposes to authorize the 

Siskiyou County Department of Agriculture (SCDA) and the CDFA to implement weed eradication 

practices on National Forest System (NFS) lands within the Salmon River District. The California 

Food and Agriculture Code Sections 403, 482, 5021, and 5405 provide the authority for eradication 

and/or suppression of noxious weeds within California. 

The Klamath National Forest, in cooperation with participants in the Siskiyou County Weed 

Management Area, will coordinate and conduct weed management practices. This will include ongoing inventory of existing and new populations; public education and information on noxious weed 

identification, methods of spread and prevention measures; and monitoring of treated areas to 

determine effectiveness of control methods and to identify additional future treatment needs. 

Temporary road closures and area closures in some infested areas will be implemented during 

treatment and following treatment to limit potential disturbance and spread of seeds. Road 

maintenance practices (grading, stock piling of materials, transport of road material, etc.) will also be 
4 SALMON RIVER Knapweed Environmental Assessment 

evaluated and adjusted to limit spread of weeds. Timing and location of livestock use in infested 

areas will also be adjusted. 

The duration of this project is anticipated to be at least five years. Implementation of this proposed 

action will begin in the spring of 2001. Eradication will only be accomplished after a considerable 

sustained effort; therefore it is important to evaluate progress on an annual basis. The Siskiyou 

County Weed Management Area representatives will participate in monitoring and evaluation of the 

project. 

Treatment descriptions: 

Manual Treatments 

Manual treatment includes the use of simple hand tools such as weeders, picks, screwdrivers, shovels, 

and mattocks for hand grubbing operations. Plants are then dug or pulled from the soil with as much 

of their root system as possible to prevent re-sprouting. Hand grubbing is proposed where the soil is 

loose and there are a limited number of plants in a small area. Hand grubbing will be used in areas of 

individual, isolated plants and as follow-up to herbicide treatment in areas previously treated where 

numbers of plants are limited to individuals that can be removed by hand. 

Chemical Treatments 

Chemical methods will include hand application spot spraying of contact herbicides from backpack 

sprayers that limits the area sprayed to the target plant. No aerial treatment is proposed. Chemical 

treatment with TranslineTM or Tordon 22KTM will include the area around the plant where viable 

seeds have been cast. Chemical treatment is planned for larger, densely infested areas where other 

methods (manual treatment and mulching) are not capable of eradicating the weed population. 

Chemical treatment is proposed for at least five consecutive years depending on the results of 

effectiveness monitoring. Individual sites may be treated up to two times in a given season depending 

on the efficacy of the initial treatment. It is anticipated that after the initial chemical treatment, other 

methods such as hand grubbing would be adequate to eradicate some populations. 

Proposed treatments will be designed that will provide maximum eradication potential while 

balancing the site-specific resource concerns. Minimizing resource impacts will be the primary 

criteria for selection of herbicides used. The type of chemical treatments will account for proximity 

to water and riparian areas, season of use, plant life-cycle stages, and other non-target vegetation 

concerns. 

The proposed herbicides and their maximum application rates are found in Table 1. The herbicides 

listed in Table 1, with the exception of Tordon 22KTM, are approved by the Environmental Protection 

Agency (EPA) for use on NFS lands in the State of California. TordonTM (picloram) is currently 

being considered by the Department of Pesticide Regulations for registration for use on noxious 

weeds in the State of California. Chemicals may be used alone or in mixtures. Those listed in Table 

1 are ones that have been chosen for their effectiveness at controlling knapweed while providing 

maximum protection of resources. These herbicides will be used as site conditions dictate. On-going 

effectiveness monitoring will determine the need for follow-up treatments. Chemicals will only be 
SALMON RIVER Knapweed Environmental Assessment 5

mixed if the mixture is not prohibited by either label and if the ingredients are compatible and 

enhance the overall efficacy of the treatment. 

In addition to the specific herbicides, the additive R-11, and a colorant Hi-Light Blue will be utilized. 

R-11 is a spreader/activator that improves the activity and penetration of the herbicide by reducing 

surface tension, allowing the herbicide mixture to spread evenly over the surface of the vegetation. 

The colorant is added to indicate where the herbicide has been applied. 

Table 1. Proposed Maximum Herbicide Application Rates. 

Chemical Name Trade Name 

Rate: Active 

ingredient per acre1

(a.i./ac). 

Acid equivalent/acre2

(AE/ac) 

Weeds and/or Areas 

Treated 

2,4-D 

Weedone 638TM and 

Weedone LV-4TM 

Weedar 64TM 

2.8 lbs a.i./ac 

1.4 AE/ac 

Upland and floodplain 

Clopyralid TranslineTM 0.250 lbs. AE/ac, a.i./ac Upland 

Glyphosate Rodeo 64TM 3.0 lbs AE/ac 

4.0 lbs. a.i./ac Riparian 

Picloram Tordon 22KTM 0.025 – 0.05 lbs a.i./ac, 

AE/ac Upland3

1 Active ingredient (a.i.) – The component in the herbicide formulation primarily responsible for its phyto-toxicity. 

Identified as such on the label. 

2 Acid Equivalent (AE) – The threshold yield of parent acid from the active ingredient that is formulated as a derivative of 

acid. 

3

 The use of picloram is not currently authorized in the State of California. This chemical will be used only if pending 

registration takes place prior to or during implementation. 

The target weeds and the treatment proposed, including optimum growth stage and season of 

application, are listed in Table 2. 

Table 2. Proposed Weed Treatment and Timing. 

Weed Treatment1 

Application rate/acre 

Growth Stage Timing2 

Weedone 638TM: 4 pt Bolt to flower Late spring/summer 

TranslineTM: 2/3 pt Mid-bolt to late bud, 

rosette, active growth Summer/fall 

Tordon 22KTM: 1-2 pt Bud to full flower Spring/late summer 

Weedar 64TM: 2-4 pt Active growth Spring/late summer 

Knapweeds 

RodeoTM: 6 pt Active growth Spring/late summer 

1 Treatment given is for a range of application rates per acre, for the listed Trade Name herbicide and are not to exceed the 

maximum rates listed in Table 1. 

2 Timing of control will include re-treatment of re-growth. 

Selection of herbicides to be used involves a step-by-step process that considers the site conditions 

(soil properties, rainfall regime, and plant life-cycle) and persistence of the chemical in the soil to 
6 SALMON RIVER Knapweed Environmental Assessment 

effectively control re-growth from seed in the seed bank. Soil active herbicides must incorporate into 

the seed germination zone of the soil profile to be effective and are generally tied up there by 

adsorption to fine soil particles and organic matter. The movement of herbicides is influenced by 

mobility (based on chemical properties), water, and adsorption. 

Habitat descriptions and proposed chemical treatment: 

Upland Areas 

The upland habitat for Knapweeds can be described as those areas upslope from riparian zones of the 

Salmon River and its tributaries. Within this area the use of more persistent herbicides will be 

prescribed. Chemicals such as picloram and clopyralid have the necessary persistence and selectivity 

to be the most effective choice for treatment in upland areas where water and riparian habitats are not 

affected. The advantages of using these herbicides are that the treatment is more effective and limits 

the number of times the area will be retreated. Picloram (Tordon 22KTM) is specific to knapweed and 

provides a high level of efficacy. It is effective only on broadleaf vegetation and will not affect native 

grasses. Clopyralid (TranslineTM) is also effective on knapweeds and is moderately persistent. The 

Weedone formulation of 2,4-D (Weedone 638TM) is proposed for use in combination with picloram 

(Tordon 22KTM) or clopyralid (TranslineTM) to enhance the efficacy of the treatment. 

Floodplain Zones 

Floodplains can generally be described as the area between the stream and its annual high water line. 

The largest known infestation of Spotted Knapweed within the Salmon River District exists within 

the floodplain of the North Fork of the Salmon River. The least persistent herbicides (glyphosate 

(Rodeo 64TM) and the amine formulation of 2,4-D) will be used in the floodplain area where the intent 

is to minimize any opportunity for residual chemicals to be present in the soil and wash into the 

watercourse during high water flows. Herbicides selected for these areas are those approved for use 

because they are proven to have the lowest potential impacts to water and aquatic species and related 

habitat. The application of herbicides in these areas will occur after the last high water event of the 

season, with ample time allowed for chemical degradation prior to the first high water event of the 

next year. It is anticipated that chemical treatment in the floodplain zone would occur from May 

through July. RodeoTM is a preparation of glyphosate specifically formulated for applications directly 

over water. It is applied to actively growing plants and will not continue to be present in the soil to 

inhibit re-growth. It is a non-selective herbicide, and kills or damages most plants it comes in contact 

with. Mitigation measures during application will minimize exposure to non-target plants. Some 

formulations of 2,4-D (Weedar 64TM) can be used in close proximity to water and have the advantage 

of being selective for broadleaf plants. 2,4-D (WeedarTM) is proposed to be used in combination with 

glyphosate (RodeoTM) in the floodplain area to enhance the efficacy of treatment 

Riparian Areas 

Riparian areas occur along the Salmon River and its tributaries. Riparian areas are described as the 

area between the annual flood zone and permanent upland vegetation occurring approximately 100 

feet above the annual flood plain. Because of the close proximity to water only those chemicals 

described above under floodplain with the short persistence intervals will be used. 
SALMON RIVER Knapweed Environmental Assessment 7

Herbicide Transport: 

It is estimated that a maximum of 16 days in one season would be required for herbicide treatment. 

The rate of application will vary by site and accessibility. It is estimated that on any given treatment 

day, the maximum amount of active herbicide ingredient to be transported in a 300 gallon capacity 

tank (or smaller depending on the area to be treated and amount of chemical to be used) would be: 2/3 

pints of TranslineTM, 2 pints of Tordon 22KTM, 21 pints of RodeoTM, and 12 pints of 2,4-D. 

Management Direction: 

Management direction relative to this project is located in the LRMP. Specific goals include 

management for desired compositional, structural, and functional attributes of biological diversity 

(LRMP pg. 4-6). Applicable Standards and Guideline located in Chapter 4 of the LRMP include 6-1, 

6-2, 6-3, 6-7, 6-11, and 6-15 (LRMP pg 4-23,4-24), 21-52, and 21-54 (pg. 4-59). 

Decision To Be Made 

The Decision to Be Made is whether to authorize weed eradication treatments in the Salmon River 

drainage and if so, to determine the design of the treatment. The decision-maker is the Salmon River 

District Ranger. 

Public Scoping and Issues 

Public scoping was initiated in January 1999. A letter was sent to the Salmon River Ranger District 

NEPA mailing list. Due to an overwhelming response to the letter, a Knapweed Project mailing list 

was created, including all respondents to the initial scoping letter. A second letter was sent to this 

list, which included a question and answer set in response to scoping comments. A public 

informational meeting was held in Forks of Salmon on February 24, 1999, to provide information on 

knapweed, the status of the project, and to answer questions. An open house was held in Forks of 

Salmon River on April 28, 1999, to present alternatives and solicit public input. 

Scoping revealed a number of issues. Key issues are most relevant to the analysis and are used to 

formulate alternatives and analyze environmental effects. Non-key issues are issues that are outside 

the scope of the analysis or decision to be made. Non-key issues do not drive alternatives and are not 

carried through the analysis process. Documentation of all comments and issues received in response 

to scoping is on file at the Salmon River Ranger District office. 
8 SALMON RIVER Knapweed Environmental Assessment 

Key Issues 

 

1. Effects to Human Health and Safety: Concern was expressed that use of herbicides in the 

Salmon River watershed would have adverse impacts to residents and visitors to the area; 

chemical herbicides pose health risks that cannot be mitigated. 

Issue Measure: Risk Assessment (risk of exposure, Hazard Quotient (HQ)). 

2. Effects to Water Quality and Aquatic-Related Species: Concern was expressed that use of 

herbicides in the Salmon River watershed will adversely affect water quality, fish, and other 

riparian and aquatic-related species. The concern was for the effects of herbicides entering the 

watercourse during or after treatment and the effects of herbicides on aquatic species. 

Issue Measure: Risk of exposure; soil adsorption potential; chemical breakdown in the 

environment, toxicity to fish, and aquatic organisms. 

3. Effects to Non-target species including plants, wildlife, insects, amphibians, fungi, 

microorganisms, and others: Concern was expressed that herbicides would have harmful effects 

to all species other than targeted weeds. 

Issue Measure: Risk of Exposure, Toxicity levels 

4. Effects to Federally listed Threatened, Endangered, Proposed, and Forest Service Sensitive 

species (TESP): Concern was expressed that herbicides will adversely affect TESP species.

Issue measure: Risk of Exposure, toxicity levels 

5. Effects to local community well being and quality of life: Local citizens expressed concern that 

their unique rural lifestyles and quality of life would be adversely affected by the use of synthetic 

chemical herbicides. Most local residents attempt to lead a lifestyle, which is relatively free from 

synthetic chemicals, and view the Salmon River environment as pristine. Use of herbicides may 

be perceived as a violation of these lifestyle principles.

 

Issue Measure: Does the alternative use chemicals or not? Yes/No 

6. Adverse Effects from the use of 2,4-D: Particular concern was expressed over the use of 2,4-

D. There is strong local opposition to the use of this chemical in the Salmon River watershed

because 2,4-D is often associated with 2,4,5-T (both were used in combination as the active 

ingredients in Agent Orange). Although the contaminant (TCCD) responsible for health risks 

associated with Agent Orange, is not found in 2,4-D, there is heightened sensitivity to use of this 

chemical because of the association.

Issue Measure: Does the alternative use 2,4-D or not? Yes/No

7. Chemical herbicides should only be used as a last resort: Many individuals and groups 

indicated that they were opposed to the use of chemical herbicides until all other reasonable 

means of eradication had been exhausted. There is disagreement over the determination of the 

effectiveness of treatment methods. Some members of the public expressed that they would 
SALMON RIVER Knapweed Environmental Assessment 9

reluctantly support the use of herbicides if it was shown to be the only effective method of 

treatment. 

Issue Measure: Does the alternative consider alternative approaches to herbicide use and a 

means of measuring effectiveness? Yes/No

Non-key Issues 

1. Use of herbicides versus other methods is uneconomical: It was suggested that an economical 

analysis of alternatives be incorporated into the project that would consider the cost of litigation. 

Costs of knapweed treatments have been calculated and are disclosed in Chapter 3. The cost of 

litigation would vary greatly and cannot be reasonably determined.

2. Use of Herbicides will destroy the biological diversity in the Salmon River watershed: The 

proposed level of herbicide use is 15-30 acres (less than .01% of the total watershed area) in 

which individual plants would be treated. It is not likely that this would have a significant impact 

on biological diversity within overall watershed. It is anticipated that control of knapweed would 

retain the biological diversity that is at greater risk if knapweed is allowed to spread uncontrolled. 

3. Consider treating all noxious weeds in the Salmon River watershed; develop a 

comprehensive plan for weed management in the area: There is an interest in having the 

Forest Service treat all noxious weeds in the area as part of this project. This project intentionally 

is focusing on Knapweeds, as they are relatively newly established and highly aggressive plants. 

Knapweeds must be treated promptly to prevent them from becoming as prevalent as other weeds 

have become in California, and as knapweed is in the inter-mountain West. Eradication of 

knapweed at this stage is feasible, while it may not be for some of the other weeds in the area. 

The Siskiyou County Weed Management Area group is interested in a larger scale noxious weed 

management strategy that includes other weeds of concern in the area, such as yellow star thistle, 

dyer’s woad, and Scotch broom. While treatment of all noxious weeds is a high priority for all 

participants in the MOU, this project is specific to knapweed. Opportunities exist to amend the 

Watershed Analyses on the Forest, and to amend the Klamath National Forest LRMP to address 

noxious weed management at a larger scale. This project is consistent with the overall 

management direction in the LRMP and the ROD. Development of a larger scale strategy, while 

desirable by all parties, is outside the scope of this site-specific assessment. 

Chapter 2. Alternatives

Alternatives Considered in Detail 

Actions common to all action alternatives: 

Standard Operating Procedures and Mitigation Measures 
10 SALMON RIVER Knapweed Environmental Assessment 

a. The Klamath National Forest will issue a letter of authorization to the Siskiyou County 

Department of Agriculture to conduct weed management practices on NFS lands. The Standard 

Operating Procedures as described below will be included and strictly adhered to. 

b. The Agriculture Commissioner will ensure that all workers are trained in identification of 

proper growth stage of noxious weeds for treatment. 

c. Periodic compliance checks of the weed management activities will be conducted by the Forest 

Service, especially when they occur around sensitive areas. 

d. A monitoring and evaluation program for determining how well treatment objectives are met 

will be developed by members of the Siskiyou County Noxious Weed Management program to 

assess the annual progress of the Integrated Weed Management Program. 

e. The North Coast Regional Water Quality Resources Control Board (NCRWQCB) will 

participate in the development of proposed water quality monitoring plans. 

f. Applicable Best Management Practices (BMPs) will be implemented and concurrently 

monitored (see Appendix B). 

g. Federal law, regulations, and direction define the management and preservation of historic 

properties as elaborated in the Antiquities Act of 1906, National Historic Preservation Act of 

1966, as amended, National Environmental Policy Act of 1969, Archaeological and Historic 

Preservation Act of 1974, American Indian Religious Freedom Act of 1978, Archaeological 

Resources Protection Act of 1979, Native American Graves Protection and Repatriation Act of 

1990, and in Executive Orders 11593, 13007, and 13082. Procedures for compliance are given 

in 36 CFR 60, 61, 63, 67, and 800. All required procedures will be followed in implementing 

this action. If cultural resources are located during implementation of the project an 

archaeologist will be notified to address resource protection. 

Mitigation Measures Specific To Chemical Methods 

a. Ground applications of liquid herbicides in the floodplain will be limited to spraying the target 

weeds. Application of TranslineTM or Tordon 22KTM in upland sites will include and the 

surrounding ground for approximately 10 feet in diameter. Backpack applications of liquids 

will occur only at low nozzle pressure and within 2.5 feet of the ground. 

b. Environmental conditions will be monitored by USFS, CDFA, or County to insure herbicide 

placement is on or immediately surrounding the target plant. Spraying shall be terminated if 

excessive wind speed or temperature inversion conditions develop. Ground applications of 

liquids or granular material will not be conducted in winds in excess of 5 mph for RodeoTM 

and 10 mph for Tordon 22KTM at the point of discharge. 

c. Mixing and/or loading of any herbicide is prohibited within one hundred and fifty (150) feet 

of any body of water. Mixing will take place at the SCDA pesticide facility in Yreka. Mixed 

products will be transferred to ground sprayers or backpack sprayers at the job-site. Spill kits 

will available on site. Any unused mix will be returned to Yreka. 
SALMON RIVER Knapweed Environmental Assessment 11

d. All herbicide mixing, loading, and application equipment shall be kept in good repair to 

prevent any spillage. All equipment shall be inspected by the SCDA prior to the first usage of 

the year, and periodic inspections throughout the application season. 

e. Spillage of any dry herbicide formulations shall be immediately cleaned up and placed in the 

application equipment for application upon the site being treated. Spillage of any liquid 

herbicide formulations or solutions shall be immediately reported to the USFS and the County 

Agricultural Commissioner. Spills will be treated according to established protocols. Refer 

to Spill Plan in Appendix C. 

f. All pesticide containers will be triple rinsed at the mix load site, and the rinsate will be added 

to the mix tank and applied at the job site. 

g. Ground equipment for liquid pesticide applications shall have nozzles with an orifice not less 

than 1/16-inch in diameter (or equivalent) and operated at a boom pressure not to exceed 30 

pounds per square inch or low pressure fan nozzles with a fan angle number not larger than 80 

degrees and fan nozzle office not smaller than 0.2 gallon per minute flow rate (or the 

equivalent) and operated at a boom pressure not to exceed 15 pounds per square inch. 

h. All applicators will be trained annually by a Certified applicator regarding the safe and proper 

use of herbicides. 

i. All herbicide applications will be made by a Certified Applicator or by persons in the direct 

supervision of a Certified Applicator. 

j. All herbicide label requirements will be followed.

k. All areas treated with chemical herbicides will be posted according to State law. Areas treated 

with herbicides will be posted during and after application and through the summer season.

l. All applicators will wear protective equipment. Clothing will be washed daily. Clean soap 

and water will be on site for routine washing of hands and face and for emergencies. 

m. Workers will be trained in safety and emergency procedures. 

n. A suitable buffer from the edge of the water will be used to prevent water contamination. 

Spray will not be applied to or allowed to drift onto any water surface at any time during 

application. 

Mitigation Measures Specific To Manual Methods 

a. All workers will wear protective clothing appropriate for the elements. 

b. Workers will check clothing and footwear prior to leaving infested sites and remove any seed 

material or soil that may contain seed. 
12 SALMON RIVER Knapweed Environmental Assessment 

c. Seeded plant material will be bagged and transported to the SCDA disposal site. 
SALMON RIVER Knapweed Environmental Assessment 13

Other Actions Common to All Action Alternatives 

• Implement appropriate road maintenance practices; evaluating rock, sand, and gravel sources; 

inspection and appropriate treatment of equipment and crews entering the area from high risk 

areas; appropriate management of permitted livestock and pack and saddle stock; signing, 

public information, and education; revegetation, inventory, and monitoring of knapweed sites. 

Areas will be closed to public use during and following treatment.

Alternative 1. The Proposed Action 

The Proposed Action is described in detail in Chapter 1 and summarized below (see Tables 1 

and 2). 

• Implement an integrated pest management program to eradicate infestations of knapweed in 

the Salmon River drainage as described previously in Chapter 1. 

• Herbicide treatment could potentially be used over all treatment acres, including the 

floodplain and upland sites. Isolated and individual plants may be removed manually. Up to 

two treatments in one season on any given site depending on efficacy of initial treatment. 

Treatment for up to five consecutive seasons depending on efficacy. 

• Chemicals to be used may include one or more of the following (see Tables 1 and 2): 2,4-D 

(Weedar 64TM) and glyphosate (RodeoTM) on up to 14 acres on the river bar and clopyralid 

(TranslineTM), picloram (Tordon 22KTM) and 2,4-D (WeedoneTM) on up to one acre in the 

upland. Selection of chemicals will include all label restrictions and requirements, 

consideration of plant growth stage, season, weather, proximity to water, soil properties. 

• All special resource considerations/mitigations identified through the interdisciplinary process 

and through interagency consultation for aquatic or terrestrial species habitat requirements, 

cultural/heritage resources, or other special status areas will also be applied as described in 

Chapter 1. 

Alternative 2. Community Based Alternative 

This alternative is a community based, cooperative venture proposed by the Salmon River 

Restoration Council. This alternative proposes an integrated pest management strategy that 

would emphasize alternatives to the use of chemical herbicide treatment (see Table 4). 

• Emphasize mechanical treatment, prevention, monitoring, and inventory and fully explore 

alternative approaches to chemical treatment on all treatment acres. 

• Treatments will include hand grubbing and digging, mulching, propane torching, and 

establishment of native vegetation. Sites will be inventoried and treated several times 

throughout the growing season. Live plants will be pulled and left on site if in a vegetative, 

pre-flowering condition, bagged and removed from the site if seed is present. 
14 SALMON RIVER Knapweed Environmental Assessment 

• Multiple treatments per site each season depending on efficacy of initial treatments. Inventory 

and treatment of all sites for at least 12 years to prevent flowering, seeding, re-sprouting, and 

spread. 

• Objectives include: a) prevent at least 95% of adults plants (each year) from seeding (increase 

this by 1% per year for 5 years). b) eliminate over 95% of all plants at all known satellite 

population sites (increase by 1% per year) c) remove 75% of plants (adults and juveniles) at 

the larger, denser, and more populated sites (i.e. Kelly Bar) and increase by 3% per year for 8 

years. 

• Revegetate 5% of sites annually on appropriate sites with native plants. 

• Preventative measures as described in Alternative 1 will be fully explored and implemented. 

• Education, monitoring, and inventory will be conducted cooperatively with all parties 

involved. 

• Citizens may “adopt a site” for long-term control and monitoring to ensure areas are 

“knapweed-free” over time.

Table 3. Alternative 2 Mechanical Treatment.

Areas Treated 

Method Growth Stage Timing 

Acres 

Riparian and 

Hand pulling, Upland 

digging, etc. 

Rosette to early 

bolt; bolting stage 

and flowering 

stage 

Spring/early 

summer 

15-30 acres 

Riparian Mulching Rosette Spring/early 

summer 0.03 acres 

Riparian and 

Re-vegetation Upland Spring/late 

summer 1-5 acres 

Alternative 3. Modified Proposed Action 

This alternative was developed in response to public input on the Proposed Action. This alternative 

responds to Issue Number 7; there is disagreement over the determination of effectiveness of 

treatment methods and support for herbicides being used only as a last resort after exhausting all nonchemical methods (see Table 4). This alternative proposes use of mechanical treatment of knapweed 

on all sites unless any one of the established evaluation criteria (see below) is not met. If evaluation 

criteria are not met, herbicide treatment will commence on any site. 
SALMON RIVER Knapweed Environmental Assessment 15

• Manual treatment of knapweed on all sites. Treatments will include hand grubbing, digging, 

mulching, and establishment of native vegetation. Sites will be inventoried and treated 

several times throughout the growing season. Live plants will be pulled and left on site if in a 

vegetative, pre-flowering condition, bagged, and removed from the site if seed is present. 

• Multiple treatments per site each season depending on efficacy of initial treatments. Inventory 

and monitoring of selected sites annually to determine efficacy of treatment. Non-chemical 

manual methods will be utilized unless it is determined that objectives cannot be met using 

established criteria. Treatment for up to 10 consecutive seasons depending on efficacy of 

treatment. 

• Evaluation criteria are: a) All established evaluation sites must show a decrease of greater 

than, or equal to, 60% in the number of plants from the previous year; b) No plants at any site 

(evaluation sites and all others) will be allowed to flower and produce seed; c) Mapped 

populations will not increase in size through spread of seed from adjacent sites. 

• An independent contractor following protocol developed by University of California, Davis 

Agricultural Extension will conduct evaluation of treatment effectiveness to determine if 

evaluation criteria are met. District Ranger will make the final determination based on site 

evaluation results provided by the contractor. 

• Evaluation sites may not be manipulated prior to May 15 of each year or evaluation will be 

invalidated and chemical use may proceed. 

• Herbicide treatment may be used on any site if one or more of the eradication criteria are not 

met on any site after the first year. 

• Chemicals to be used may include (see Tables 4 and 5): glyphosate (RodeoTM), clopyralid 

(TranslineTM), or picloram (Tordon 22KTM). Selection of chemicals will follow all label 

restrictions and requirements, consideration of plant growth stage, season, weather, proximity 

to water, and soil properties. 

• In addition to the specific herbicides, the additive R-11, and a colorant Hi-Light Blue will be 

utilized. R-11 is a spreader/activator that improves the activity and penetration of the 

herbicide by reducing surface tension, allowing the herbicide mixture to spread evenly over 

the surface of the vegetation. The colorant is added to indicate where the herbicide has been 

applied. 

• Up to two chemical treatments may occur in one season on any site depending on efficacy of 

initial treatment. District Ranger and Siskiyou County Agricultural Commissioner will 

determine initial treatment efficacy. 

• Standard Operating Procedures and Mitigation Measures as described in Alternative 1. 
16 SALMON RIVER Knapweed Environmental Assessment 

Table 4. Alternative 3 Treatment of Knapweeds 

Timing2 Areas Treated Trade Name 

(chemical) Treatment1 Growth Stage No. of 

treatments Acres 

Spring/early 

summer 

Riparian 

Mechanical Rosette to early 

bolt 3/year 15-30 acres 

Late 

spring/summer 

TranslineTM 2/3 pts 0.25 Upland 

AE/ac 

0.25 lbs a.i./ac 

Mid-bolt to late 

bud; active 

growth 2/year 1 acre 

Spring/early 

summer 

RodeoTM Riparian 7.5 – 6 pts 

3.0 AE/ac 

4.0 lbs a.i./acre 

Active growth 

2/year 15-30 acres 

Spring/late 

summer 

Tordon 22K Upland 

(picloram) 

1 –2 pts .5 

AE/ac 

0.5 lbs a.i./ac 

Bud to full 

flower 2/year 15-30 acres 

Spring/fall Re-vegetation 1/year Up to 30 acres 1

 Treatment is for a range of application rates per acre for the listed Trade Name herbicide and all rates 

are less than maximum rates listed on the herbicide label. 

2

 Timing of control will include treatment of re-growth. 

Alternative 4. No Action Alternative 

No action will be taken to reduce or eliminate knapweed in the project area. 
SALMON RIVER Knapweed Environmental Assessment 17

Comparison of Alternatives 

Refer to Tables 5 and 6 for a comparison of the Alternatives. 

Table 5. Acres By Treatment Type. 

Alternative Glyphosate 

(RodeoTM) 

Clopyralid 

(Transline

TM) 

or 

Picloram 

(Tordon 

22KTM) 

Glyphosate 

(RodeoTM) 

& 2,4-D 

(WeedarTM) 

Clopyralid 

(TranslineTM) 

or Picloram 

(Tordon 22KTM) 

& 2,4-D 

(WeedoneTM) 

Manual 

Treatment 

(Grubbing, 

digging, 

mulching, 

and 

revegetation) 

1 15-30 acres 1 acre < 1 

2 Up to 30 acres 

3 Up to 25 

acres 

Up to 5 

acres Up to30 acres 

4 

Table 6. Alternative Comparison. 

Issue 

(Measure) 

Human Health 

and Safety 

(Risk/Toxicity) 

Water Quality 

Aquatic Effects 

(Risk/Toxicity) 

Non-Target 

Species and 

TESP 

(Risk/Toxicity) 

Use of 2,4-D 

(Yes/No) 

Community 

Life-style 

Impacts 

(Yes/No) 

Duratio

n of 

Time to 

meet 

Eradication 

Meets 

Purpose and 

Need 

Potential for 

eradication 

(High/Med/ 

Low) 

1 Slight to 

Moderate 

None to 

Slight 

 Slight to 

moderate Yes Yes 4 years High 

2 None to 

Slight 

None to 

Slight 

None to 

Slight No Yes 10 years 

Low 

3 Slight None to 

Slight 

None to 

Slight No Possible 4-10yrs Med 

4 None Slight None to 

slight None Yes N/A Not at all 

Alternatives considered, but not in detail: 

Alternative 5. Non-synthetic herbicides - corn gluten 

Corn gluten meal is a by-product of corn that was discovered at the University of Iowa as a nonsynthetic herbicide treatment that suppresses emergence of some plants at certain application 

rates. Studies indicate that up to 500- 800 pounds per acre (20 to 60 lbs or more/1000 sq. ft.) of 

the product is necessary to achieve desired results. Literature on the product indicates that it is 
18 SALMON RIVER Knapweed Environmental Assessment 

approximately 10% nitrogen (N) by weight. There is no post emergence control of weeds. If 

plants have germinated or formed roots, they will not be controlled by corn gluten. 

Corn gluten has been used in limited applications and appears to be best suited for lawn and turf 

management. Corn gluten has not been tested on knapweed or in wildland conditions such as 

those present in the Salmon River area. The efficacy of treatment on established plants of this 

species in meeting objectives is questionable at this time. Further more, there is concern that the 

high application rates and the nitrogen content would have adverse effects on aquatic habitat if 

used in the floodplain area. Suppressing establishment of desired native plants does not meet 

LRMP goals for biological diversity. 

This alternative does not meet purpose and need of eradication. 

Alternative 6. High temperature steam treatment. 

High temperature steam machines have been used in some areas to kill undesirable live plants in 

conjunction with railroad right-of ways and in nursery situations. This technique was designed 

more for roadside eradication in areas of easy vehicle access. The large equipment required is not 

suited for off-road or mountainous terrain. This alternative was not considered to be practical or 

effective to meet the objectives at this time. 

This alternative does not meet purpose and need of eradication. 

Alternative 7. Biological control 

Biological control is not a method used for eradication of noxious weeds and is not considered 

effective at the known level of infestation at this time. The purpose of introducing biological 

controls to infestations of noxious weeds is to reduce those infestations to tolerable levels. Since 

knapweed is considered a public nuisance and an “A” rated pest, the acceptable tolerance is zero. 

Biological control is used to attempt to contain large infestations of pests and prevent the rate of 

spread from increasing. 

This alternative does not meet the purpose and need of eradication of this knapweed at this 

time. 

Chapter 3. Environmental Consequences

Issue-Related Consequences 

Issue 1 - Effects to Human Heath and Safety 

Environmental consequences relative to this issue will be discussed for each alternative. This issue 

will be evaluated through a hazard analysis and an exposure analysis. Hazard will be measured in 

terms of a Hazard Quotient (HQ) which compares estimated doses to an established reference dose. 

The analysis will consider the risk of exposure to the public and to workers applying herbicides and 
SALMON RIVER Knapweed Environmental Assessment 19

the anticipated dose levels the public and workers might be exposed to given the proposed rates of 

application and the dosages likely to result from the estimated exposures. 

A Human Health and Safety Risk Assessment (Bakke, 2000) was completed for this project to assess 

the site-specific risks to human health and safety from using the herbicides proposed for use 

(Appendix A). The analysis is based on the actual planned herbicide application rates shown in Table 

1. The site-specific risk assessment uses standard methodology widely accepted by the scientific 

community, regulatory agencies, and the Forest Service (USDA, 1989, referred to as FEIS, pages 4-

62 to 4-122 and Appendix f; National Research Council (NRC), 1983; United States Environmental 

Protection Agency (EPA), 1986; Syracuse Environmental Research Associates, SERA 1996; 1997, 

1999a, 1999b). In essence, the risk assessment compares herbicide doses that people might receive 

from applying the herbicides (worker doses) or from being near an application site (public doses) with 

doses shown to cause no observed ill effect (No Observed Effect Levels, NOEL) in test animals and 

long-term laboratory studies. The risk assessment examines the chance, based on site-specific 

herbicide use levels, that exposures from these herbicide formulations would result in acute, systemic, 

or reproductive effects. The site-specific risk assessment also examines the potential for these effects 

to cause synergistic effects, cumulative effects, and effects on sensitive individuals including women 

and children. 

Herbicides are intended to be toxic to plants. They are intended to interfere with vital plant processes 

that do not occur in animals: seed germination, hormone-mediated growth and development, and 

photosynthesis. Basic biological and physiological differences between plants and animals partly 

account for the relatively low toxicity of most herbicides to animals. 

The main impacts on human health from chemical treatments depend upon the toxicity of the 

chemical and the level of human exposure. All chemical effects of biological systems follow a doseresponse relationship; as dose increases so does effect and vice versa. The chemicals proposed for 

use in this assessment have not been found to cause significant mutagenic or carcinogenic effects. 

Hazard Analysis 

Hazard analysis requires gathering information to determine toxic properties of each herbicide. 

Human hazard levels are primarily derived from results of lab experiments on animal models, 

supplemented where appropriate with information on human poisoning accidents, epidemiological 

studies, and data on chemical structure. 

The types of toxicity levels generally considered are systemic and reproductive. Systemic toxicity is 

observed as acute through chronic. Acute toxicity studies are used primarily to determine the toxicity 

reference point (i.e. lethal dose) of a given substance. Chronic toxicity studies are designed to 

characterize dose-response relationships resulting from repeated exposure to a compound over time. 

Reproductive and developmental studies are conducted to determine the effect of a chemical on 

reproductive success. Reproductive studies are most often multi-generational. 

Toxic effect levels (acute) are often expressed as LD50, the dosage of toxicant (expressed in 

milligrams of toxicant per kilogram of animal body weight) required to kill 50 percent of the animals 

in a test population when given orally. Toxicity of herbicides and other substances is displayed for 

information purposes in Table 7. Toxicity (chronic) can also be expressed in terms of NOELs 
20 SALMON RIVER Knapweed Environmental Assessment 

defined as: (1) the lowest dose of a substance by any route other than inhalation that has been found 

by experiment with animals to have no toxic effect on the animals, or (2) the lowest concentration of 

a substance in the air that has been found by experiment with animals to have no toxic effect on the 

animals exposed for a defined time. 

Chemical exposure may be brief (acute) or prolonged (chronic). The terms acute and chronic may be 

used to describe duration of effect as well as duration of exposure. The kind of response (acute or 

chronic) observed in organisms depends on the route of intake (oral, dermal, inhalation) and 

frequency of exposure, coupled with the specific mechanisms of toxicity. A chemical of high toxicity 

may represent no or limited hazard if exposure and dose are low, just as a chemical of limited toxicity 

may be hazardous if exposure is high. 

Extensive studies of the absorption, distribution, metabolism, and excretion of herbicides in animals 

(SERA, 1996, 1997, 1999a, 1999b) have shown that the herbicides in this document and their 

metabolites are rapidly eliminated from most animals and do not substantially accumulate in animal 

tissues. These traits further reduce the possibility that exposure will result in harmful adverse 

consequences. 

Of concern is the probability that the use of a chemical will result in an irreversible effect such as 

reproductive or genetic effects. Reproductive effects include infertility miscarriage, general fetal 

toxicity, and birth defects (teratogenesis). Almost all chemicals will produce reproductive effects in 

the laboratory at some dose. 

Table 7. Acute Toxicity Classification Acute Toxicities of the Four Herbicides and Other 

Chemicals. 

Toxicity Category Herbicide or Other 

Chemical Substance 

Oral LD50 for Rats 

(mg/kg) 

Equivalent Human 

Dose 

Very Slight 5,000 – 50,000 More than 1 pint 

Sugar 30,000 

Kerosene 28,000 

Ethyl Alcohol 13,700 

Diesel Oil 7,380 

Simzine >5,000 

Slight 500 – 5,000 1 ounce to 1 pint 

Glyphosate 4,320 

Clopyralid 4,300 

Picloram 4,012 

Table salt 3,750 

Bleach 2,000 

Aspirin, Vitamin E 1,700 

Moderate 50 - 500 1 teaspoon to 1 ounce 

2,4-D 375 

Caffeine 200 

Severe 0 – 50 1 teaspoon or less 

Nicotine 50 

Parathion (insecticide) 13 
SALMON RIVER Knapweed Environmental Assessment 21

 Botulinus Toxin 0.00001 

Reference: R-5 FEIS (USDA, 1989) 

All anticipated herbicide exposures in the analysis will be compared to a reference dose (RfD). 

Exposure to hexachlorobenzene, an impurity contained in two of the herbicides proposed for use, is 

compared to a Minimum Risk Level (MRL). The U.S. Environmental Protection Agency establishes 

an oral RfD for registered pesticides that is an estimate of a daily dose to a human that is likely to be 

without appreciable risk of deleterious effects during a lifetime (EPA 1989). It uses the lowest 

systemic NOEL from the most relevant species and studies. The NOEL is divided by a factor 

(usually 100) to determine RfD to account for variation in species. 

The risk assessment compares herbicide doses expected from application (worker doses) or from 

being near the site (public doses) with doses shown to cause no observed ill effect (NOEL). The risk 

assessment examines the chance, based on site-specific herbicide use levels, that exposures from 

these herbicide formulations would result in acute, systemic, or reproductive effects. The risk of 

threshold effects was evaluated in terms of a HQ, which compares the expected doses to the RfD. If 

the HQ is less than one, it indicates a low human health risk. The site-specific risk assessment also 

examines the potential for these treatments to cause synergistic effects, cumulative effects, and effects 

on sensitive individuals, including women and children. 

Risk Analysis 

Those potentially at risk fall into two groups: workers and members of the public. The most likely 

individuals to be exposed to herbicides during and after the project are the backpack applicators 

applying the treatments; residents who live near the treatment areas and visit the sites; hikers and 

backpackers; hunters; fishers; nature students; native plant materials collectors; swimmers and rafters; 

and firewood gatherers. Dispersed use in the area would range from 5 to 20 people per year in some 

of the remote upland sites, to up 200 or more people per year on the accessible river bar sites. 

There are 7 occupied residences within 1⁄4 mile of any of the proposed treatment units (the Relative 

Toxicity Level of Herbicides is listed in Table 8). Drift of spray when using backpack sprayers to 

spray individual plants under the specified wind conditions (less than 5 mph) will not reach the 

residences and effects are expected to be negligible. Herbicide application equipment is designed to 

cover target plants with a minimum of off target spray movement, or drift. Despite the effectiveness 

of application equipment used, some small fraction of the droplets may break into smaller droplets 

that the wind could blow off-site. Hand application techniques proposed are not broadcast sprays and 

will not produce any appreciable herbicide drift. Granular and pelletized formulations are also 

associated with little drift. Several studies have been conducted to determine spray drift; various 

sources for assumptions and methods of calculations have been consulted (USDA 1984). In the 

studies, spray drift at distances downwind of the application site was determined for aerial, backpack, 

and ground mechanical application equipment. Spray drift from hand application equipment was 

determined to be negligible. 

Specific mitigation measures are planned for the project alternatives that will further reduce risks to 

workers and the public. These include use of protective clothing, washing clothes daily. Clean soap 

and water for routine washing of hands and face and for emergencies will be on site. Workers would 

be trained in safety and emergency procedures. 
22 SALMON RIVER Knapweed Environmental Assessment 

In addition, risk of exposure is relatively low due to several other factors including protective buffers, 

wind restrictions for spraying, signing and posting areas that are sprayed, using a colored dye in the 

spray, and restricting access to units that have been treated. 

In addition to the site-specific risk assessment in Appendix A, discussion of effects of alternatives to 

human health and safety incorporates by reference information contained in several documents that 

were used as a basis for analysis. These documents are available in the project file at the Scott River 

Ranger Station in Fort Jones, CA. Toxicity information for the herbicides being considered for use is 

summarized in the Pesticide Background Statements, Volume 1 Herbicides (Forest Service 

Agricultural Handbook, No. 633 (USDA, 1984)), in the FEIS and in risk assessments completed for 

the proposed herbicides by the (SERA, 1996; SERA, 1999a, SERA 1999b.). Risk Assessment For 

Herbicide Use In Forest Service Regions 1,2,3,4, and 10 and On Bonneville Power Administration 

Sites (USDA, 1992). 

Table 8. Relative Toxicity Level of Herbicides.

Glyphosate 2,4-D Picloram Clopyralid 

Trade Name RodeoTM; 

RoundupTM 

WeedarTM, 

WeedoneTM 

Tordon 22kTM TranslineTM 

LD50 (mg/kg) 1 2,000 –6,000 300 - 2000 3,000 – 5,000 27 - >5,000 

Commonly Used 2

Terms/Toxicity 

Category 

Slightly toxic Moderately to 

slightly toxic Slightly toxic Slightly toxic 

Activity in soil 

Inactivated upon 

contact with the 

soil. 

Leached in sandy 

soil; breakdown 

depends on 

microbial activity. 

Sorption by 

organic matter and 

clays; may leach in 

sandy soils. 

Active in soil; not 

absorbed, highly 

soluble. Rapid 

breakdown by soil 

microbes. 

Hazard Quotient 

(HQ)4 0.014 2.9 0.030 0.006 

Systemic/Reproductive NOEL3

(mg/kg/day) 

20/50 31/3 7/50 15/75 

1

 Most LD50 values are expressed as a range to account for differences in experimental conditions, the type of carrier the 

toxicant is dissolved in, or the species of test animal used. 

2

 Severely Toxic is LD50 less than 50 mg/kg, Moderately Toxic is 50–500 mg/kg; Slightly Toxic is 500-5,000; Very Slightly 

Toxic is 5,000-15,000 mg/kg (or higher); relatively non-toxic is more than 15,000 mg/kg in a single oral dose to rats based on 

EPA toxic categories (Maxwell 1982). 

3

 The highest dosage level at which no reproductive effects have been observed in test animals, including decreased fertility, 

reduced litter size, reduced offspring, size or poor viability (reproductive) and fetus malformations during development; not 

associated with genetic change (teratogenic). 

4

 The Hazard Quotient is the estimated dose divided by the RfD. An HQ < 1 indicates a low human health risk. HQs shown 

here are for worker doses. Exposure to the general public would be expected to be less. See the Risk Analysis in Appendix A 

for all public exposure scenarios and associated HQs. 
SALMON RIVER Knapweed Environmental Assessment 23

Characteristics of Proposed Herbicides in Alternatives 1 and 3 

Glyphosate 

The toxicity of glyphosate is relatively well characterized in humans and experimental mammals. 

The acute toxicity of glyphosate is relatively low, with LD50 values in experimental mammals ranging 

from 2,000 to 6,000 milligrams/kilogram of body weight (mg/kg). Most of the data regarding human 

exposure to glyphosate involves consumption of large quantities of glyphosate during attempted 

suicide studies. Glyphosate is not a primary skin irritant and is only minimally irritating to the eye. 

There is no evidence that glyphosate is a teratogen (causes birth defects) (SERA, 1996). Some 

formulations of glyphosate contain an impurity, N-nitrosoglyphosate (NNG), considered a 

nitrosamine. EPA concluded that the NNG content of glyphosate was not toxicologically significant 

in terms of carcinogenicity. NNG is not present in the formulation (RodeoTM) proposed for use in this 

project. 

Two general exposure assessments were used in the SERA Risk Assessment (SERA, 1996): jobspecific assessments and incident assessments. Job-specific assessments estimate the absorption 

associated with relatively complex job activities, such as mixing, loading, and applying glyphosate. 

All of the assessments give a range based on application rates, empirical observations of variability in 

exposure rates, and number of acres estimated to be treated per hour. 

Workers, compared with the general public, are exposed to greater levels of glyphosate. Typical 

ground workers are exposed to 0.0005-0.073 mg/kg. Members of the general public are usually 

exposed to only extremely low levels of glyphosate (0.00012-0.007 mg/kg), except for accidental 

exposures scenarios when exposure levels may approach levels for occupational exposure (0.007-

0.019 mg/kg). 

The current RfD for glyphosate is 2.0 mg/kg/day (U.S. EPA 2000), which is based on a NOEL of 175 

mg/kg/day with an uncertainty factor of 100 used to account for species-to-species extrapolation and 

sensitive subgroups. 

Clopyralid 

Clopyralid (TranslineTM) has a low order of acute toxicity, with acute LD50 values in the range of 

2,700 to greater than 5,000 mg/kg. After direct instillation into the eye, clopyralid (TranslineTM) can 

cause persistent damage to the eye (redness, swelling opacity of the iris). Clopyralid is neither a skin 

irritant nor a skin sensitizer. Studies have shown no systemic toxic effects from dermal exposure. On 

chronic or sub-chronic exposures, no effects have been observed in laboratory mammals at doses of 

50 mg/kg/day or less, which EPA has identified as the systemic NOEL. The RfD for clopyralid 

(TranslineTM) is 0.5 mg/kg/day. Studies have not shown any reproductive or teratogenic effects at 

levels below that which would be maternally toxic. Clopyralid (TranslineTM) is not a mutagen and 

studies have shown it not to be a carcinogen. 

There are two impurities in the clopyralid (TranslineTM) formulation: hexachlorobenzene [nominal 

concentrations of less than 2.5 parts per million (ppm)] and pentachlorobenzene (nominal 

concentrations of less that 0.3 ppm). Hexachlorobenzene has been identified by the EPA as a 
24 SALMON RIVER Knapweed Environmental Assessment 

probable human carcinogen, and is a persistent environmental contaminant. The RfD is established 

as 0.0008 mg/kg/day. Data on pentachlorobenzene is insufficient to classify as a potential 

carcinogen. 

According to the SERA Risk Assessment (1999), the amount of hexachlorobenzene released each 

year in Forest Service programs nationally is about 0.0034 kg. It concluded that Forest Service 

programs contribute very little to background levels of hexachlorobenzene in the environment 

(approximately one part in one-hundred million parts). In normal applications of clopyralid 

(TranslineTM), workers will be exposed to greater amounts of hexachlorobenzene than the general 

public. Nonetheless, the central estimates of worker exposure under normal conditions to 

hexachlorobenzene are below the background levels of exposure by factors of about 3 to 5. The 

report concluded that there is no basis for asserting that the use of clopyralid (TranslineTM) by the 

Forest Service will result in substantial increased in the general exposure of either workers or 

members of the general public to hexachlorobenzene. 

Picloram 

Picloram (Tordon 22KTM) has a low order of acute toxicity, with acute oral LD50 values in the range 

of 3,000 to 5,000 mg/kg. Picloram (Tordon 22KTM) is classified as a moderate eye irritant, but as a 

non-irritant to the skin. The systemic NOEL is 20 mg/kg/day. This is the basis for EPA’s calculated 

RfD, which is 0.2 mg/kg/day. The low chronic toxicity may be due in part to the fact that picloram 

(Tordon 22KTM) is rapidly excreted from the body. Picloram is not a mutagen, and EPA has 

classified picloram (Tordon 22KTM) in Group E (no evidence of carcinogenicity) based on the lack of 

such activity in tested rats and mice. 

There is an impurity in the picloram (Tordon 22KTM) formulation, hexachlorobenzene, which has 

been identified by EPA as a probable human carcinogen (see discussion above). 

2,4-D 

2,4-D can be classified as moderately toxic in rats with an oral LD50 of 375 mg/kg (EPA 1987). The 

acute dermal LD50 of 2,4-D in rabbits is greater than 3,980 mg/kg (EPA 1987). Several primary eye 

irritation studies in rabbits have been conducted with various 2,4-D products. Toxic effects range 

from severe to slight. EPA (1990) established an RfD for chronic oral exposure to the herbicide 2,4-

D of 0.01 mg/kg/day, with a NOEL of 1.0 mg/kg/day. 

2,4-D ingestion or skin exposure in humans can cause irritation of the gastrointestinal tract, chest 

pain, and muscle twitching. Ingestion of large does of 2,4-D causes gastroenteritis, skeletal and 

cardiac myotonia (abnormal muscular movement), and central nervous system depression in humans. 

A human dose of 80 mg/kg of the dithylamine salt of 2,4-D caused congestion of all organs, 

degeneration of nerve cells, and death. Accidental swallowing of 110 mg/kg of the isooctyl ester of 

2,4-D caused muscle twitching and paralysis, although the individual recovered in 24 hours (cited in 

USDA 1984). 

Toxicological and Epidemiological Studies of 2,4-D 
SALMON RIVER Knapweed Environmental Assessment 25

The toxicology of 2,4-D has been extensively investigated, primarily because 2,4-D was used in 

combination with 2,4,5-T as the active ingredients in Agent Orange. A major issue is the 

contamination of Agent Orange with TCDD, which is a contaminant of 2,4,5-T. There are no reports 

in the literature that 2,4-D contains TCDD as a contaminant. While 2,4-D and 2,4,5-T are structurally 

similar (differing by one chlorine atom), the difference is extremely important making the probability 

of 2,4-D containing TCDD remote. 

The two formulations proposed for use in Alternatives 1 and 3 are an ester amine salt (WeedarTM) and 

an ester formulation (WeedoneTM). The ester formulation contains 2,4-D concentrations that are 

higher than those found in the salt formulation. There is substantial uncertainty in the exposure 

assessments and risk characterizations for the different formulations of 2,4-D. There is less 

uncertainty of the dose-response relationships for the acid salts and esters. 

Several epidemiological investigations have been conducted to examine the link between human 

exposure to phenoxy acid herbicides and cancer. In the mid and late 1970s, Hardell and colleagues 

(Hardell and Sandstrom 1979; Eriksson et al. 1981; Hardell et al. 1981) conducted a series of casecontrol studies in rural Sweden. These studies found a significant increase (five- to six-fold) in the 

relative risk of soft tissue carcinomas, Hodgkin’s disease, and non-Hodgkin’s lymphoma among 

farmers using various herbicides. However, many experts have questioned the validity of the studies’ 

results because of possible selection bias, observation bias, and uncontrolled confounding variables. 

A Swedish study found no significant increase in the relative risk of soft-tissue sarcomas in 

agricultural and forestry workers exposed to phenoxy herbicides (Wilklund and Holm 1986). A casecontrol study in New Zealand found no increased relative risk of soft tissue carcinomas (Smith et al. 

1984). A multitude of studies has been conducted investigating this link. These studies were 

reviewed thoroughly by the U.S. EPA and are undergoing additional review as part of the reregistration process for 2,4-D scheduled for the year 2000. The cancer risk assessment for 2,4-D 

should be examined after the re-registration process is completed. 

Effects of Alternatives 

Effects to human health and safety will be disclosed by alternative and by herbicides used in 

Alternatives 1 and 2. The data used is taken from the Human Health and Safety Risk Assessment 

prepared for this project (Appendix A). Herbicide doses were calculated for the Proposed Action for 

workers and potentially exposed members of the public. For analysis purposes in this EA, the worker 

doses and associated HQs are used as a basis of comparison of alternatives. Under normal situations 

(i.e. non-accidental) risks to applicators are higher than risks to the general public because workers 

have a greater potential for exposure to the herbicides. In the Risk Assessment, HQs were calculated 

for a number of scenarios. Many of the scenarios are accident scenarios that do not approximate 

expected doses estimated in the proposed action and alternatives. They are analyzed in the risk 

assessment to display a relative range of effects under varying conditions. A Hazard Quotient less 

than one is considered to be an acceptable risk. HQ is based upon a comparison of a single daily 

exposure with an acceptable lifetime daily exposure level. 

Alternative 1 

This alternative proposes the use of up to four herbicides: glyphosate (RodeoTM), 2, 4-D (both an 

amine and ester form), clopyralid (TranslineTM), and picloram (Tordon 22KTM; soluble 
26 SALMON RIVER Knapweed Environmental Assessment 

concentrate) on 15 to 30 acres. All sites could potentially be treated with herbicide application. 

The majority of herbicide treatment sites (80% or more) occurs in the river bar and would be 

treated with a combination of glyphosate and 2,4-D. The upland sites would be treated with 

picloram or clopyralid. Based on the Risk Assessment (Appendix A), 2,4-D poses a moderate 

risk to human health and safety; glyphosate, picloram, and clopyralid pose slight risks. HQs for 

each proposed chemical are displayed below. This alternative poses a moderate risk to human 

health and safety. 

Glyphosate (RodeoTM) 

The estimated worker dose1 for this alternative is: 0.018 mg/kg/ of body weight/day. 

The RfD is: 2.0 mg/kg/day. 

The HQ is: 0.009 

At the estimated rate, the HQ for workers is considerably less than one. General public exposure 

would be less than that. Use of glyphosate in this alternative represents little risk of acute or 

chronic effects. It poses a very slight risk to human health. 

Clopyralid (TranslineTM) 

The estimated worker dose for this alternative is: 0.002 mg/kg/day. 

The RfD is: 0.5 mg/kg/day 

The HQ is: 0.004 mg/kg/day 

At the estimated rate, the HQ is considerable less than one. Use of clopyralid in this alternative 

represents little risk of acute or chronic effects. It poses a very slight risk to human health. 

Picloram (Tordon 22kTM) 

The estimated worker dose for this alternative is: 0.004 mg/kg/day. 

The RfD is: 0.2 mg/kg/day. 

The HQ is: 0.020 mg/kg/day 

At the estimated rate, the HQ is considerable less than one. Use of picloram in this alternative 

represents little risk of acute or chronic effects. It poses a very slight risk to human health. 

Hexachorobenzene2

The estimated worker dose for this alternative is: .000000036 mg/kg/day 

The RfD is: 0.0008 mg/kg/day 

The HQ is: 0.000006 mg/kg/day 

At the estimated rate, the HQ is considerably less than one. Use of hexachlorobenzene in this 

alternative represents little risk of acute or chronic effects. It poses a very slight risk to human 

health. 

2,4-D (Weedar 64, Weedone638) 

The estimated worker dose is: 0.02 mg/kg/day. 

The RfD is: 0.01 mg/kg/day. 

The HQ is: 2.0 mg/kg/day. 

 

1

 Uses an established absorbed dose rate times the application rate. 

2

 Hexachlorobenzene is an impurity found in both Clopyralid and Picloram 
SALMON RIVER Knapweed Environmental Assessment 27

At the estimated rate, the HQ is greater than one. Use of 2,4-D in this alternative represents some 

risk of acute or chronic effects. It poses a moderate risk to human health. 

Alternative 2 

This alternative does not propose the use of any chemical herbicides for treatment of knapweed. The 

threat of risk to human health and safety from use of herbicides is eliminated. 

There is some risk of injury to workers in this alternative due to extensive use of manual methods of 

removal of knapweed. This could be in the form of back injury from prolonged bending and digging, 

over-exposure to sun and other elements, tripping and falling and cuts or abrasions from use of hand 

tools. This risk would be slightly higher than in Alternatives 1 and 3 due to the more extensive and 

repeated treatment required when using manual methods only to eradicate knapweed. It is expected 

that these risks would be minimized with the use of protective clothing and gloves and by 

implementing standard safety precautions during field work. This alternative poses a very slight 

risk to human health and safety. 

Alternative 3 

This alternative proposes the use of up to three herbicides: glyphosate (RodeoTM), clopyralid 

(TranslineTM) and picloram (Tordon 22KTM; soluble concentrate) if manual methods are determined 

not to meet established evaluation criteria. 2,4-D will not be used in this alternative. For purposes of 

analysis of the effects of this alternative, it was assumed that up to 30 acres could be treated with 

herbicides. 

Use of glyphosate, clopyralid, and picloram represents little risk of acute or chronic effects. 

The discussion of the effects of the three chemicals to be used in this alternative and their effects to 

human health and safety is the same as discussed in Alternative 1. 

There is some risk of injury to workers in this alternative due to the use of manual methods of 

removal of knapweed as discussed in Alternative 2. This alternative poses a slight risk to human 

health and safety. 

Alternative 4 

No action would be taken in this alternative, and workers and the public would not be exposed to 

chemical herbicides or manual labor. This alternative poses no risk to human health and safety. 

Effects Common to Alternatives 1 and 3 

Synergistic Effects 

Synergistic effects (multiplicative) are those effects resulting from exposure to a combination of two 

or more chemicals that are greater than the sum of the effects of each chemical alone (additive). 

Instances of chemical combinations that cause synergistic effects are relatively rare (FEIS, pg 4-112). 

Synergism has not been observed in toxicological effects involving combinations of commercial 

pesticides. 
28 SALMON RIVER Knapweed Environmental Assessment 

The herbicide mixtures proposed in Alternatives 1 and 3 have not shown synergistic effects in 

humans who have used them extensively in forestry and other agricultural applications. However, 

synergistic toxic effects of herbicide combinations, combinations of the herbicides with other 

pesticides such as insecticides or fertilizers, or combinations with naturally occurring chemicals in the 

environment are not normally studied. In one study, a mixture of 2,4-D and picloram produced skin 

irritation in test animals while neither herbicide alone has been shown to cause this effect (USDA, 

1989). 

Based on the limited data available on pesticide combinations, it is possible, but quite unlikely, 

that synergistic effects could occur as a result of exposure to the herbicides considered in this 

analysis. Even if synergistic effects or additive effects were to occur as a result of treatment, these 

effects are dose responsive (Dost, 1991). This means that exposures to the herbicide plus any other 

chemical must be significant for these types of effects to be of biological consequence. 

Based on the very low exposure rates estimated for the alternatives, any synergistic or additive 

effects are expected to be insignificant. 

Cumulative Effects 

The proposed use of herbicides in the two alternatives could result in cumulative doses of herbicides 

to workers or the general public. Cumulative doses to the same herbicide result from (1) additive 

doses resulting from various routes of exposure from this project, and (2) additive doses resulting 

from various routes of exposure to other herbicide treatments. Each of the hazard quotients 

summarized in Table 8 involves a single exposure scenario. In some cases, individuals could be 

exposed by more than one route, and in such cases can be quantitatively characterized by simply 

adding the HQs for each exposure. The risk of this is greater for workers than for the general public, 

unless the public is using significant amounts of herbicides for home use. There are no major 

adjacent landowners in the Salmon River area that have used herbicides or plan to use herbicides in 

the future. The Forest Service has not used herbicides in the area for over 10 years. 

Since these herbicides persist in the environment for only 1 to 12 months (FEIS, 4-9), do not 

bioaccumulate, and are rapidly eliminated from the body (SERA, 1996, 1997, 1999a, 1999b), it is not 

anticipated that any additive herbicide doses from re-treatment in following years would occur. 

Even in the unlikely event of multiple exposures to the herbicides proposed for use over a period of 

one day or for several months, the associated HQs when added together would remain below one and 

therefore pose a low health risk to those individuals. 

Cumulative effects from the herbicides proposed in Alternatives 1 and 3 will not result in 

substantial cumulative effects to human health and safety. 

Sensitive Individuals 

The margin-of-safety (MOS) used in the development of the RfD takes into account much of the 

variation in human response. The normal MOS of 100 is sufficient to ensure that most people will 

experience no toxic effects (R5 –FEIS, pg.4-114). “Sensitive” individuals are those that might 
SALMON RIVER Knapweed Environmental Assessment 29

respond to a lower dose than average, which includes women and children. Factors affecting 

individual susceptibility to the herbicides include diet, age, heredity, preexisting diseases, gender, and 

life-style. Individual susceptibility to the herbicides proposed in this project cannot be specifically 

predicted. Unusually sensitive individuals may experience effects even when the MOS is equal to or 

greater than 100. Both alternatives require the posting of sprayed units and area closures to avoid 

contact during and immediately after spray. This should effectively prevent adverse effects to 

sensitive individuals. Because these chemicals rapidly decay in the environment, and because they 

will not be applied to water or move substantially through the air or soil, the probability of exposure 

is low and the time frame for risk of exposure would be limited to several months. 

Because only a very small portion of the public is likely to be exposed to these applications, and 

because except in extremely unlikely public exposure scenarios analyzed in the Risk 

Assessment, the HQ values are generally much less than 1 for public exposure, adverse effects 

to the public are not expected. 

Inert Ingredients, Impurities, Additives, and Metabolites 

The toxicity data are based on the active ingredients found in the herbicide formulations. The 

formulations also include chemicals, called inert ingredients, which act as carriers for the active 

ingredients and facilitate the effective application of the herbicides. Other spray additives such as 

surfactant R-11 and/or colorants may be added to mixtures prior to application. Concern was 

expressed about the possible toxic properties of the inert ingredients and the full formulations during 

public scoping. 

Inert Ingredients 

Table 9 lists the percentages of inert ingredients found in the herbicide formulations being considered 

for use in the alternatives. The primary ingredient in RodeoTM is water; in TranslineTM is isopropyl 

alcohol; and in Tordon 22KTM is Polyglycol 26-2. There is little published information on the 

impurities in commercial formulations of 2,4-D. Studies conducted in the 1970s (SERA, 1997) 

reported that commercial samples contained concentrations of monochlorophenoxyacetic acid (0.1%), 

dichlorophenoxyacetic acid (2.3%), 2,4,6-trichlorophenoxyacteic acid (0.2%), and bis (2,4-

dichlorophenoxy) acetic acid (0.7%). 

Table 9. Percentage of inert ingredients present in herbicide formulations. 

Chemical Formulation EPA Reg. # % Inert 

Glyphosate RodeoTM 534-343 46.2 (water) 

Clopyralid TranslineTM 62719-259 59.1 (isopropyl alcohol) 

Picloram Tordon 22KTM 62719-6 75.6 (polyglycol 26-2) 

2,4-D Weedar 64TM 71368-1-264 53.2 (none on EPA list) 

2,4-D Weedone 638TM 71368-3-264 61.7 (petroleum 

distillates/xylene) 

The EPA has categorized approximately 1,200 inert ingredients into four lists (FEIS, 4-116; Fed Reg. 

54:48314-16). For a more detailed discussion of the inert ingredients and their potential effects see 

the Risk Assessment in Appendix A. Lists 1 and 2 contain inert ingredients of toxicological concern. 

List 3 includes substances for which EPA has insufficient information to classify as either hazardous 

(List 1 and 2) or non-toxic (List 4). Use of formulations containing inert ingredients on Lists 3 and 4 
30 SALMON RIVER Knapweed Environmental Assessment 

are preferred Forest Service policy. The inert ingredient in TranslineTM is on list 4. The inert 

ingredient in Tordon 22KTM is on List 3. The lack of information on this compound and with the 

inert ingredients contained in the Weedone formulation of 2,4-D adds an element of uncertainty to the 

Risk Assessment (SERA, 1999b, Bakke 2000). 

Comparison of acute toxicity (LD50 values) data between formulated products (including inert 

ingredients) and their active ingredients alone shows that the formulated products are generally less 

toxic than their active ingredients (FEIS, USDA 1984). 

While these formulated products have not undergone chronic toxicity testing like their active 

ingredients, the acute toxicity information on the inert ingredients in each product leads to the 

conclusion that the inert ingredients in these formulations do not significantly increase the health risk 

over the risks identified for the active ingredients. Health risks from inert ingredients and the full 

formulations of the proposed treatments are low; some uncertainty exists in the Weedone 

formulation of 2,4-D. 

Impurities 

As stated above, both picloram and clopyralid contain the impurity hexachlorobenzene. In addition, 

clopyralid contains the impurity pentachlorobenzene. Glyphosate contains the impurity Nnitroglyphosate (NNG) and 2,4-D may contain impurities discussed above. As stated in SERA 1996, 

1997, 1999a, 1999b, concern for impurities in technical grade products is reduced by the fact that the 

existing toxicity studies on these herbicides were conducted with the technical grade product. The 

carcinogenic risk of the impurity hexachlorobenzene as shown above is very low. 

Additives 

The surfactant R-11® is a spreader/activator that improves the activity and penetration of the 

herbicide by reducing surface tension, allowing the herbicide mixture to spread evenly over the 

surface of the vegetation. A colorant, Hi-Light BlueTM, is used to mark the areas sprayed and 

maximize the efficiency of application. The ingredients in these products are considered proprietary. 

The Superfund Amendments and Reauthorization Act (SARA) list none of the ingredients as 

hazardous. The dye is commonly used in toilet bowl cleaners and as a colorant for lakes and ponds. 

Information in the site-specific Risk Assessment for this project (Appendix A) was obtained from 

EPA and the manufacturers. Based on the chemical nature of the ingredients, the risk assessment 

concludes only very slight toxicity is expected. The use of additives in the formulation would 

result in almost no increase in risk to the health and safety of the workers or public. 

Metabolites 

Metabolites are compounds formed as a result of metabolism or biochemical change. The assumption 

is that the toxicological consequences of metabolism in the species on which toxicity studies are 

available will be similar to those in humans. Uncertainties in this assumption are encompassed by 

using an uncertainty factor deriving the RfD and may sometimes influence the selection of the study 

used to derive the RfD (SERA, 1999a). 

Clopyralid (TranslineTM) has been shown to not be extensively metabolized in rats, with most of the 

dose being excreted unchanged in the urine within 24 hours. Similarly in plants, clopyralid remains 

unchanged in the plant. (SERA 1999a). 
SALMON RIVER Knapweed Environmental Assessment 31

The primary metabolite of glyphosate (RodeoTM) is aminomethylphosphonate (AMPA). In mammals, 

only a very small amount of AMPA, less than 1% of the absorbed dose, are formed. AMPA is poorly 

absorbed in the gastrointestinal tract and is eliminated primarily in the urine (SERA, 1996). 

As reviewed by the EPA, there is no indication that picloram is extensively metabolized (SERA, 

1999b). 

2,4-D does not appear to be metabolized extensively in mammals; however, the compound degrades 

in the environment to form the metabolite 2,4-dichlorophenol, which is a toxic metabolite. The RfD 

for 2,4-dichorophenol is 0.003 mg/kg/day. Because there is no indication that workers or the general 

public will be exposed to substantial amounts of 2,4-dichorophenol, the formulation of this 

compound in sediment as part of the environmental degradation process does not contribute 

substantially to risks associated with the use of 2,4-D in the alternatives (SERA, 1997). 

One study done in the Pacific Northwest Region on National Forest lands, found that of 254 samples 

representing 133 sprayings of 2,4-D, 117 had no confirmable residues, 13 had residues less than 5 

ppb, two had residues of 5-10 ppb, and one had a residue of 40 ppb (Neisess 1983 as cited by USFS 

1984). All of these are well below public health goals. 

Issue 2 - Effects to Water Quality and Aquatic-Related Species. 

This section will discuss and analyze the potential effects of the alternatives on watershed conditions 

and processes using measures of risk and toxicity. Of specific concern are the effects of herbicides on 

soil and water quality, the potential for water contamination and impacts on aquatic-related resources. 

One specific objective is to determine whether this project will comply with the NCRWQCB’s 

“Water Quality Control Plan for the North Coast Region” (3/24/1994). This will be discussed further 

at the end of this section. 

The riparian areas proposed for treatment are the alluvial flats and gravel bars along the Salmon 

River. Overall, these units are underlain by sand and gravel alluvium deposited by the Salmon River. 

A few of the units have some soil development on old sand bars. 

The Kelly Gulch units are located along and just below the top of a rocky ridge. These units are 

underlain by forest soils that contain fine particles and organics. There is no surface water near any of 

these treatment units. 

Water Quality Effects 

The potential impact of herbicide treatment of knapweed on water quality and fisheries is a major 

concern. Although in the past improper application of insecticides have generally caused 

substantially more fish and wildlife concerns, careful analyses of herbicide application projects and 

their effects is an important consideration in water quality protection. 
32 SALMON RIVER Knapweed Environmental Assessment 

Characteristics of Proposed Herbicides in Alternatives 1 and 3 

The chemical structure of each herbicide is important because it influences whether the chemicals 

would be immobilized, degraded, or possibly transported into the aquatic environment. The behavior 

of a chemical in soil is determined by a number of properties related to both the chemical and the soil 

environment. Chemical substances that are adsorbed to soil particles are mostly degraded in place 

and resist leaching. Adsorption of chemicals to soil particles depends primarily on the clay and 

organic content, temperature and pH of the soil. 

Chemical substances in the soil are subject to degradation by sunlight, chemical, and biological 

means, and movement by diffusion, dissolution, or vaporization. Many soil organisms are capable of 

metabolizing chemical substances. Biological degradation is an important means by which 

substances are removed from the soil. 

Glyphosate (RodeoTM): 

Glyphosate adsorbs strongly to fine particles in the soil (Monsanto, 1997; EPA, 1993; SERA, 1996), 

and is not expected to move vertically below the six-inch soil layer (EPA, 1993). It has a half-life of 

30 to 40 days in the soil. Soil microbes readily break down glyphosate to AMPA, which is degraded 

to CO2 (EPA, 1993). AMPA also strongly absorbs to soil particles (EPA, 1993). If glyphosate were 

to reach surface water, it would not be broken down readily by water or sunlight (EPA, 1993); 

however concentrations in natural water will diminish rapidly due to microbial degradation, binding 

to suspended particulates, or dispersion (SERA, 1996). Monsanto (1997) states on the label that the 

biological degradation process will occur under both aerobic and anaerobic conditions by soil 

microflora. 

 

The NCRWQCB has not established a water quality standard for Glyphosate. However, the 

California Department of Public Health has established a standard of 700 PPB for drinking water. 

Although the Salmon River is not used for drinking water, all waters of the state are considered to 

have this beneficial use and so this standard applies. 

Clopyralid (TranslineTM): 

Clopyralid is applied as a liquid spray to foliage. The proposed formulation, TranslineTM, contains 

clopyralid plus a surfactant. TranslineTM is active in the soil, is not absorbed by the soil, and is highly 

soluble. Its propensity for leaching is offset by the fact that it is broken down very rapidly by soil 

microorganisms. TranslineTM has an average half-life in the soil of 25 days (SERA, 1999). 

Several studies have looked at leaching, runoff, and degradation of clopyralid in soil (Baloch and 

Grant 1991a, Baloch and Grant 1991b, Smith and Aubin 1989, Pik et al. 1977, Elliott et al. 1998, 

Baloch-Haq et al. 1993 Bergstrom et al. 1991, as cited by SERA 1999). The most relevant study for 

quantitatively assessing runoff and leaching potential appears to be Elliott et al. (1998, as cited by 

SERA 1999). The Elliott et al. study was designed as a worst-case scenario of clopyralid mobility. In 

the period between day 9 and 35, only 1.5% of the applied amount was washed off. The predominant 

factor in the functionally low rate of both leaching and runoff is rapid degradation in the soil column 

(Baloch-Haq et al. 1993, Bergstrom et al. 1991, as cited by SERA 1999). Woodburn and French 

(1987 as cited by SRA 1999) also found that the potential for clopyralid to runoff from surface 

erosion with rains is relatively low. 
SALMON RIVER Knapweed Environmental Assessment 33

As discussed in the Human Health and Safety section above, clopyralid contains a trace contaminant, 

hexachlorobenzene. In most formulations of TranslineTM, it is present in very small amounts. 

Hexachlorobenzene is a known carcinogen that is ubiquitously present in the environment. 

The potential for adverse effects on non-target aquatic species appears to be remote (SERA 1999). 

Research suggests that no adverse effects are plausible using the typical, or even worst-case, exposure 

assumptions. Neither the NCRWQCB nor the California Department of Public Health (CDPH) has 

established a water quality standard for TranslineTM. 

Picloram (Tordon 22KTM): 

Picloram (Tordon 22KTM) will be applied as a foliar spray on and around the target plants and in the 

immediate area of seed cast. 

Picloram is another chemical that is highly soluble in water, however unlike clopyralid, it is resistant 

to both biotic and abiotic degradation processes (EPA 1995). Picloram is stable to hydrolysis and 

anaerobic degradation and degrades very slowly with half-lives ranging from 167 to 513 days (EPA 

1995). However, Wauchope et al. (1992 as cited by EXTOXNET 1996) found field half-lives from 

20 to 300 days, with an estimated average of 90 days. In some soils, picloram is almost completely 

resistant to all degradation processes. 

Photodegradation is one form of degradation picloram can go through; however, it is only significant 

on the soil surface (Weed Science Society of America 1994, as cited by EXTOXNET 1996). In 

laboratory studies, picloram in water was readily broken down by sunlight, with a half-life of 2.6 days 

(Howard 1991, and Weed Science Society of America 1994, as cited by EXTOXNET 1996, EPA 

1995). Picloram is expected to be persistent in surface water except in clear shallow water with 

substantial mixing, or with waters with short hydraulic residence times (EPA 1995), such as the 

Salmon River. 

The NCRWQCB has not established a water quality standard for Tordon 22K TM. The CDPH has 

established a public health goal of 500 parts per billion (ppb) for picloram. This goal applies to water 

that is being consumed daily by humans. 

2,4,D (WeedarTM, WeedoneTM): 

In soils, 2,4-D generally has a short (1 month or less) persistence (Ashton 1982 as cited by USFS 

1984). It tends to be mobile and is primarily degraded by microbial activity. In the aquatic 

environment, 2,4-D is readily degraded by microbial activity, which, along with dilution, is the major 

means for its loss of activity in aquatic systems (USFS 1984). 

In general, 2,4-D is relatively mobile in soil, although this mobility is strongly influenced by various 

factors such as water solubility of the specific formulation and organic content, and pH of the soil. 

Despite its relative mobility, 2,4-D is not thought to leach into streams (Norris 1981 as cited by 

USFS). In two separate studies, Norris et al. (1982) and Suffling et al. (1974) found less than 0.02% 

of the 2,4-D applied to a watershed appeared in stream flow (Norris et al. 1991).

The half-life of 2,4-D in soil is less than seven days (EXTOXNET, 1996). It is also taken up from the 

soil by plants for a short period, further reducing its potential to contaminate ground water. 
34 SALMON RIVER Knapweed Environmental Assessment 

WeedarTM is the formulation proposed for application to the populations of knapweed along the 

Salmon River, in combination with glyphosate (RodeoTM). The upland sites, where the ester 

formulation WeedoneTM would be applied, are limited in number and are well removed from any 

water sources. 

The CDPH has established a public health goal of 70 ppb for 2,4-D. This goal applies to water that is 

being consumed daily by humans. The NCRWQCB Basin Plan, Action Plan for Control of 

Discharges of Herbicides Wastes from Silvicultural Applications, establishes a water quality goal for 

the ester formulation of 2,4-D. It prohibits an instantaneous concentration of 2,4-D PGBE ester 

greater than 40 ppb acid equivalent or a 24-hour average of 2 ppb acid equivalent. 

Alternative 1 

This alternative proposes to accomplish eradication of knapweed with herbicides. In terms of 

water quality, treatment of the river bar sites is of primary consideration. Direct and indirect 

effects were analyzed and determined to be minimal for all chemicals proposed for use on river 

bars and uplands. Chemicals proposed for used in the uplands pose little probability of 

leaching or runoff into surface water. 

Effects of Glyphosate (RodeoTM) and 2,4-D (WeedarTM) in the Riparian Area: 

Glyphosate (RodeoTM) and 2,4-D (WeedarTM) will be applied by hand with backpack sprayers to 

approximately 15-30 acres of knapweed plants that occur within a total treatment area of about 150 

acres. Applicators will walk to each individual plant and spray the leaf surface. Herbicide will not be 

applied if wind speed is in excess of 5 mph. There will be a small amount of over-spray and drip 

from the plant that will fall on the soil surface. Siskiyou County Department of Agriculture estimates 

that 50-80% of the applied herbicide mix will strike the foliar surface and be absorbed by the plant. It 

is also possible that a very small amount of RodeoTM and WeedarTM can volatilize from the leaf 

surface and travel through the air to adjacent plants or the ground surface. It is not anticipated that 

there will be any spray that reaches the Salmon River. In addition, spraying will be ceased if there is 

a predicted Lightning Activity Level (LAL) of 2 or greater for that day.1

Direct Effects: 

Direct watershed effects would be the application or spillage of herbicide into any body of water 

within the project area at a level greater than the applicable water quality standard. No herbicide will 

be applied directly to the water. It is possible that an applicator applying herbicide could trip and fall 

during application. The spray tank is made of durable plastic and will not normally rupture from this 

kind of impact. The only herbicide that could be leaked before the operator picked up the tank would 

be a small amount through the pinhole air vent in the lid. As an emergency precaution, the Forest 

Service inspector and the county crews will carry spill equipment. 

For this alternative, the hand application of glyphosate (RodeoTM) and 2,4-D (WeedarTM) has a very 

low risk of producing any contamination of groundwater or surface water. This is based on the 

following facts 1) a very small amount of herbicide will be applied, 2) glyphosate (RodeoTM) and 2,4-

D (WeedarTM) decay very rapidly, and 3) water sampling on other National Forests in California from 

 

1

 Most rainfall in the summer occurs as isolated thundershowers. The only useful predictor of a thundershower is the 

lightning advisory issued by KNF dispatch. The indicator selected is a Lightning Activity Level (LAL) of 2 or greater. 
SALMON RIVER Knapweed Environmental Assessment 35

projects with much higher application rates has not detected herbicide in the samples. Direct effects 

from this alternative are expected to be minimal.

Indirect Effects –Runoff from a severe summer thundershower: 

The only way that herbicides proposed for use in Alternative 1 will reach the water system would be 

in a worst-case scenario situation. Under typical weather conditions in an average weather year, there 

is very little probability of glyphosate (RodeoTM) or 2,4-D (WeedarTM) being transported from the 

application site to a water body. In a normal weather year, it is usually 60 to 90 days before 

significant rain occurs from fall storms. According to weather statistics from the Western Regional 

Climate Center for the Sawyer’s Bar Ranger Station, the probability of greater than 0.1 inches 

occurring in May is 10%, June is 8%, July is 2 %, and August is 5%. Thus, there is little probability 

of rainfall occurring that would be significant enough to create surface runoff during the period of 

herbicide application. However, the Salmon River basin experiences infrequent and unpredictable 

thundershowers during the summer. An analysis of the probable concentration of glyphosate 

(RodeoTM) and 2,4-D (WeedarTM) in the Salmon River that might be produced from an intense 

summer thundershower that occurred directly over some of the application units soon after herbicide 

application is described in Appendix E. This analysis is based on a worst-case scenario, which 

describes a series of highly improbable circumstances under which herbicides could be transported 

into the water. This analysis indicates that this severe scenario could result in a concentration of 

about 2 ppb in the Salmon River. The minimum detection level (MDL) for glyphosate (RodeoTM) is 5 

ppb. Thus, even in a worse case, low-probability scenario, there is very little chance of a detectable 

level of herbicide being introduced into the Salmon River. The risk of occurrence of indirect 

effects from implementation of this alternative is minimal. 

Clopyralid (TranslineTM) and Picloram (Tordon 22KTM)

Application of Clopyralid (TranslineTM) and Picloram (Tordon 22KTM) to upland sites:

If Tordon 22KTM becomes approved for application in California, it will be used on the upland 

knapweed sites. Most of these sites are located near the top of the ridge and are underlain by normal 

forest soils containing fine particles and organics. These knapweed sites are located a long distance 

from any surface water. Due to the small amount of applied herbicide, the scattered distribution of 

the application sites and the long distance to any surface water, there is almost no risk that application 

of Tordon 22KTM will result in water contamination. 

For TranslineTM, the small amount of applied clopyralid that contacts the soil surface will be adsorbed 

by particles in the soil. Microbiological activity in the soil will rapidly degrade it to CO2 (SERA, 

1999) by the time rains occur the following fall. 

Due to the small amount of herbicide being applied, and the fact that it is being applied a long 

distance away from any surface water, there is very little probability of any of the herbicide 

leaching into groundwater or running off into surface waters. Direct and indirect effects are 

anticipated to be minimal. 

Cumulative Effects of all Herbicides: 

The only potential cumulative watershed effect is from herbicides used in this project in combination 

with other herbicide use in the Salmon River basin. Based on statements made by many local 

residents at public hearings and in scoping letters, there is little or no herbicide use by private 

residents. It is possible that residents could use commercially available pesticides on their private 
36 SALMON RIVER Knapweed Environmental Assessment 

property. The relative amount of chemical applied around a few homes in the approximately 

200,000-acre watershed is very small. The Forest Service has not used any herbicides in the Salmon 

River watershed since 1983. Cumulative effects are expected to be negligible. 

Water Quality Effects of Additives and Inert Ingredients: 

R-11® Surfactant 

Wilbur-Ellis manufactures the surfactant R-11®. It is used in the Forest Service Region-5 (the State 

of California) as a surfactant for glyphosate (RodeoTM) applications. R-11® will be added to 

glyphosate (RodeoTM) to aid in the dispersal and adsorption of the active ingredient when it contacts 

the foliar surface of the plant. Use of R-11® in the mix increases the efficacy of the herbicide, 

allowing an approximate 50% reduction in the amount of applied herbicide (Stephen Wratten, 

Monsanto Corp, personal communication). Approximately 1 quart of R-11® will be added per 100 

gallons of herbicide mix; i.e. R-11® comprises approximately 0.25 % of the applied mix, by volume. 

R-11® also contains silicates. Silicate is a naturally occurring substance that is non-toxic. The 

essential chemical ingredient in R-11® is nonylphenol polyethoxylate (NPE). Research has shown 

that in the presence of oxygen, NPE quickly biodegrades, with a lab-tested half-life of a few to 

several days (C. Naylar, Chemist, Hunstman Chemical Co., personal communication, 1999). In the 

presence of oxygen, NPE is rapidly broken down into other components, primarily carbon dioxide 

and water. In summary, based on the small amounts of applied R-11® and the probability that 

it will break down rapidly in the environment where it is being applied, it is very improbable 

that R-11® would be present in large enough concentration after herbicide application to either 

enter a water body or create adverse water quality effects. 

HI-LIGHTTM Blue Dye 

Blue dye will be added to all of the herbicide mixes so that the applied herbicide is visible. This will

aid in assuring that the herbicide is applied correctly to the target plants. The exact chemical 

composition of the commercial formulation, HI-LIGHTTM, is not known; however, the label states 

that there are no reportable quantities of hazardous ingredients or toxic chemicals present. Only very 

slight toxicity is expected. Based on the small amounts of dye proposed for use and the absence of 

toxic substances present in the blue dye, no direct, indirect, or cumulative water quality effects are 

expected.

The primary inert ingredient in glyphosate (RodeoTM) is water, in clopyralid (TranslineTM) is 

isopropyl alcohol, and in picloram (Tordon 22KTM) is polyglycol 26-2. Although these products have 

not undergone detailed testing like their active ingredients, concern for environmental effects is 

reduced by the fact that the existing toxicological studies on these herbicides were conducted with the 

technical grade product that includes the impurities. Effects to water quality are expected to be 

none to slight. 

Impurities 

Both picloram (Tordon 22KTM) and clopyralid (TranslineTM) contain the impurity hexachlorobenzene. 

In addition, clopyralid (TranslineTM) contains the impurity pentachlorobenzene. Glyphosate 

(RodeoTM) contains the impurity N-nitroglyphosate. Concern for impurities in technical grade 

products is reduced by the fact that the existing studies on these herbicides were conducted with the 

technical grade product. Effects to water quality are expected to be none to slight. 
SALMON RIVER Knapweed Environmental Assessment 37

Alternative 2: 

There are minimal direct effects to water quality as a result of this alternative.. Based on field 

observations, the mechanical treatment results in a small area of disturbed soil. Generally, the manual 

technique used disturbs a very localized site around the target plant. Usually a metal probe is used to 

loosen the soil/rock around the plant so the entire root can be extracted. The use of larger tools, such 

as a Pulaski, is discouraged but can be utilized if the probes are not available or there is a very 

localized spot of several plants. The physical watershed effect of this soil disturbance is not 

significant. 

Alternative 3 

The direct effects of manual treatment will be the same as those described in Alternative 2 

would not change for this alternative. The water quality effects of herbicide use in this 

alternative will be the same for glyphosate, picloram, and clopyralid as discussed in Alternative 

1. Though 2,4-D will not be used, the effects to water quality are expected to be similar to 

Alternative 1 because soil residence times of both glyphosate and 2,4-D are similar. 

Glyphosate (RodeoTM) 

Refer to the discussion under Alternative 1 for the effects on water quality. The potential watershed 

effects are similar to that under Alternative 1; there is a very low probability of water contamination. 

Picloram (Tordon 22KTM) and Clopyralid (TranslineTM) 

Under this alternative, the treatment and effects to water quality of the upland sites in Kelly Gulch 

with either picloram (Tordon 22KTM) or clopyralid (TranslineTM) would be the same as in Alternative 

1. 

Alternative 4 – No Action: 

There are no direct effects to water quality as a result of this alternative. Indirect effects may 

occur if eradication of knapweed is not achieved. Cumulative water quality effects could occur 

if knapweed were to spread and occupy significant acreage in the watershed. If no action is 

taken to remove knapweed plants, knapweed could eventually cover most of the area on the open 

gravel bars. Native grasses, forbs, and wildflowers will be displaced by the knapweed. The 

watershed implications of this ecological change are that knapweed will change the composition of 

the riparian vegetation along the zone and impact water quality by increased erosion resulting from 

decreased soil holding capacity of the root system (taproot). 

Water Quality Control Board Basin Plan 

The following discussion applies to Alternatives 1 and 3: 
38 SALMON RIVER Knapweed Environmental Assessment 

The Water Quality Control Plan for the North Coast Region, March 1994 (Chapter 4 - 

Implementation Plans) addresses the use of herbicides in silvicultural applications. Refer to The 

“Action Plan for Control of Discharges of Herbicides wastes from silvicultural Applications” (pg. 4-

32.00) for detailed description of objectives. The Plan does not mention either hand-application of 

herbicides or the control of noxious weeds. However, based on the assumption that this silvicultural 

plan will apply to noxious weed eradication projects, it establishes a basic framework for meeting the 

Clean Water Act through the authority of the NCRWQCB. This basic framework includes submittal 

of project information and a monitoring plan, a spill plan, and a BMP implementation plan to the 

Board. 

The Salmon River Knapweed Project differs from silvicultural projects to control competing 

vegetation for the following reasons: 

• The target vegetation, a noxious weed, actually occurs and is being spread, within the stream side 

zone; 

• The herbicides being proposed for application to this weed in the floodplain are actually EPA and 

label-approved for direct water application; 

• The herbicides will be applied by hand rather than aerially, resulting in much less herbicide being 

applied per acre. 

• With hand application by certified and experienced applicators, the application of the herbicide 

can be controlled to specifically isolate treatment to hit only the target plant. 

Summary of Potential Watershed Effects From Herbicide Application 

(Alternatives 1 and 3): 

The potential risk that this project will produce water quality contamination can best be understood 

by examining in detail the specific watershed processes that might transport herbicide from the 

application site to a water body. Those processes are: 

1. Accidental application by the applicator directly to the surface of water. 

2. Transport of herbicide vapor by air currents from the application site to a body of water. 

3. Some of the herbicide that drips onto the soil surface is leached through the soil column and into 

groundwater. 

4. Some of the herbicide that drips onto the soil surface is eroded during a rainstorm and the soil 

particles are transported into a water body. 

5. During the winter after herbicide application, the groundwater table next to the Salmon River 

rises and encounters soil under a treated plant that has a glyphosate residual. 

6. Dead knapweed plants with an herbicide residue are carried by high water into the Salmon River. 

(See Appendix E for a more detailed discussion of the above). 

In summary, the only process that has any probability of transporting herbicide into the 

Salmon River is number 4, the risk that some of the herbicide (glyphosate and 2,4-D, or 

glyphosate alone) that drips onto the soil surface will be eroded during a rainstorm and the soil 

particles transported to the Salmon River. It is extremely unlikely that any herbicide could be 

delivered to the water. Even in a worst-case summer thundershower, based on some very 

conservative assumptions, the amount would be below the detection limits. 
SALMON RIVER Knapweed Environmental Assessment 39

Effects to Aquatic Species 

Direct effects to aquatic species could occur during the treatment of the floodplain zone, possibly 

during the riparian area treatment. As discussed above under water quality, the likelihood of any of 

the alternatives to adversely affect water quality and subsequently impact aquatic-related resources is 

very low. 

The herbicides proposed for use in Alternatives 1 and 3 are characterized by relatively low aquatic 

toxicity. None of the compounds bioaccumulate in fish tissues, nor is there bio-magnification to 

higher trophic levels. Ingested herbicides are rapidly excreted. 

The potential impact of the herbicides being proposed on fish and other aquatic organisms is a 

function of two factors: 1) the toxic characteristics of the compound, and 2) the concentration to 

which the organism is exposed. The 96-hour LC50 refers to the concentration that is lethal to 50% of 

the fish exposed at that level for 96 hours. The lower the LC50 the more sensitive the species is to the 

herbicide. 

Alternative 1 

The direct and indirect effects analysis pertains to all the anadromous fish found in the Salmon River 

Sub-basin. The effects to coho salmon are potentially less than other species, due to the lower 

probability of coho currently occurring in the North Fork Salmon River where the majority of infested 

sites currently exist. 

In general, for aquatic organisms lethal effects (LC50) at concentrations below 1 part per million 

(ppm) are considered indicative of highly toxic substances; effects at concentration of 1 to 10 ppm are 

considered indicative of slightly toxic compounds (Clarke et al, as cited by USFS 1984). 

At the proposed application rate, no effect on fish, aquatic invertebrates, macrophytes, and 

most species of algae would be expected from the application of glyphosate. Clopyralid, 

picloram and 2,4-D would all have slight or no effects on these aquatic organisms. 

Glyphosate (RodeoTM) 

The characteristics of glyphosate (RodeoTM) are discussed above under Water Quality. Glyphosate 

(RodeoTM) is practically non-toxic to fish and aquatic invertebrates (see Table 10). The toxicity of 

glyphosate (RodeoTM) to aquatic species depends on the acidity (pH) of the water. Glyphosate 

(RodeoTM) is more toxic in relatively acidic waters by as much as a factor of 10. In general, LC50

values for aquatic animals range from approximately 10 to 400 mg/L, depending on species and water 

pH. 

Table 10. Observed 96-hour LC50 Values For Glyphosate. 

Fish species Water pH 6.3 pH 7.2 pH 8.2 
40 SALMON RIVER Knapweed Environmental Assessment 

Coho salmon 27 mg/L 36 mg/L 210 mg/L 

Chinook salmon 19 mg/L 30 mg/L 220 mg/L 

Rainbow trout 10 mg/L 22 mg/L 220 mg/L 

Wan et al. 1989, as cited by SERA 1996. 
SALMON RIVER Knapweed Environmental Assessment 41

Daphnia are significantly more sensitive to glyphosate than other invertebrates. The LC50 for daphnia 

is 218, mg/L, about the same as that reported for fish at comparable pH (SERA 1996). 

At the proposed application rate, no effect on fish, aquatic invertebrates, macrophytes, and most 

species of algae would be expected from the application of RodeoTM (SERA 1996). Since the 

proposed rate will be less than the maximum allowed under the label, there should be no direct 

or indirect effects to aquatic organisms from the use of glyphosate for this alternative. 

Clopyralid (TranslineTM) 

The potential adverse effects to fish from the use of TranslineTM appear to be remote (SERA 1999). 

Research suggests that no adverse effects are plausible using typical, even worse case scenarios. 

For fish, only standard 96-hour acute toxicity bioassays are available. The lowest reported LC50 for 

trout is 103 mg a.e./L. At least for aquatic species, the monoethanolamine salt form of clopyralid 

appears to be substantially less toxic than the technical clopyralid. The TranslineTM formulation of 

clopyralid is the salt. 96-hour LC50 values for the monoethanolamine salt range from 700 (rainbow 

trout) to 1,645 a.e./L. The lowest reported LC50 for aquatic algae is 6.9 mg a.e./L. No chronic studies 

for fish are available. A chronic reproductive NOEL for Daphnia has been determined at 

approximately 20 mg a.e./L (SERA 1999). Clopyralid does not bioaccumulate in fish tissues. Direct 

and indirect effects to aquatic species from the use of clopyralid are expected to be none to 

slight. 

Picloram (Tordon 22KTM) 

Picloram (Tordon 22KTM) is slightly to moderately toxic to freshwater fish and is lightly toxic to 

aquatic invertebrates. Significant bioaccumulation in aquatic organisms is not expected to occur 

(EPA 1995). Acute LC50 values for rainbow trout and Daphnia are 13 mg/L and 68.3 mg/L 

respectively. The maximum accepted concentration (MATC) for early life stage of rainbow trout is 

0.88 mg/L (EPA 1995). Acute risk for rainbow trout (steelhead trout), coho salmon, and chinook 

salmon is not low; however, the studies conducted assume a lentic water body. With the dilution 

factor of a lotic system, such as the Salmon River, the risk would be assumed to be lower. Because 

the sites selected for use of picloram are far removed from any water bodies, and as stated above, the 

anticipated runoff to any stream system is negligible. Effects, both direct and indirect, to aquatic 

species from the use of picloram (Tordon 22KTM) are expected to be none to slight. 

2,4-D (Weedar 64TM and Weedone TM)

Table 11 displaying the 96-hour LC50 values and No Effect Concentration level for 2,4–D. 
42 SALMON RIVER Knapweed Environmental Assessment 

Table 11. 2,4-D Toxicity Values For Aquatic Organisms.

2,4-D formulation/species 96-hour LC50

mg/L (ppm) 

NOEC* 

mg/L (ppm) 

Dimethylamine salt liquid 

 Rainbow trout** 100 10 

 Chinook salmon+ 100 

Daphnia** 4 0.4 

2,4-D acid 

 Pink Salmon fry# 10 

 Chum salmon fry# 50 10 (NOEL) 

 Coho salmon fry# 50 10 (NOEL) 

Butyl Ester 

 Cutthroat trout** 0.9 0.09 

* No Observed Effect Concentration 

* Norris et al. 1991 

+ Johnson and Finley 1980 as cited by USFS 1984 

# Meehan et al. 1974 as cited by USFS 1984 

LC50 values for rainbow trout and chinook (100mg/L) represent that the Weedar 64TM formulation 

that would be combined with glyphosate and applied along the Salmon River is less than slightly 

toxic (10 mg/L). Since coho salmon have similar physiologies to chinook salmon, this should also 

hold true for coho. Due to the rapid degradation of 2,4-D in soil, very negligible amounts, if any, will 

be left on site once rainfall commences in the fall. There is very little chance of stream contamination 

occurring. Effects, both direct and indirect, to aquatic species with the use of the amine 

formulation of 2,4-D are expected to be none to slight. 

The formulation of 2,4-D to be used on upland sites is Weedone LV4TM, a butoxy ethanol ester. As 

with the amine form of 2,4-D (Weedar 64TM), there should be very negligible to no herbicide 

available in/on the soil to runoff by the time fall rains begin. The very short residence time, buffer 

distance to water bodies, and its very strong adsorption properties to organic material, would result in 

very negligible to no amount available for runoff. Therefore, the greater toxicity of the butoxy 

ethanol ester formulation would not affect the anadromous fish species of the Salmon River. 

An indirect effect that could occur with the use of herbicides is removal of vegetation. However, due 

to the application technique being individual plant and not aerial, negligible non-targeted vegetation 

removal will occur. Therefore, shade and large woody material recruitment will not be affected by 

this action. In addition, negligible incidental removal of vegetation may occur in the uplands. 

Therefore, no additional sedimentation will occur due to the removal of excessive vegetative cover. 

Even if vegetative over-story were removed, the protective duff layer would still be in place. 

R-11® Surfactant 

The label for R-11® states it may be used with aquatically labeled glyphosate at 2 quarts per 100 

gallons of spray solution. 
SALMON RIVER Knapweed Environmental Assessment 43

R-11® has a nonylphenol polyethoxylate (NPE) ingredient that puts it in a broad class of chemicals 

known as alkylphenol ethoxylates (APEs). A raw material used to make NPE is nonylphenol (NP). 

NP has been shown to exhibit weak estrogenic properties in laboratory tests. In comparison to the 

natural estrogen 17-β-estradiol, NP is approximately 100,000 times weaker in eliciting estrogenic 

responses. NPE has also been found to be weakly estrogenic through lab tests, but less potent than 

NP by an order of magnitude (EPA 1996). The NPE used in R-11 has about nine ethoxylate groups 

attached (referred to NP9E) making it highly water soluble (Bakke 1999). 

Research has shown that in the presence of oxygen, NPE biodegradation is rather quick, with labtested half-life of a few to several days. In aerobic conditions NP9E is broken down by removal of 

the ethoxylate groups as a result of microbial action, into shorter-chain ethoxylates. These shortchain ethoxylates can further be broken down into nonylphenol ether carboxylate (NPEC) (APE 

Research Council 1999; EPA 1996, Maguire 1999, as cited in Bakke 1999). The basic aromatic ring 

at the center of the NPE molecule appears to break apart prior to the loss of the final ethoxylate 

groups, therefore the formation of NP is not likely (APE Research Council 1999, as cited by Bakke 

1999). 

In anaerobic conditions, NP would be produced from the breakdown of NPE. However, NP is 

adsorptive to soil organic carbon, and therefore would not likely move through the soil or stream 

sediments (EPA 1996). 

 

If the 24 hr LC50 ÷ 96 hr LC50 for a particular chemical is ≥ 2, it indicates the chemical may cause 

chronic effects (Zeeman 1995, as cited in EPA 1996). The sensitivity of rainbow trout to NP is 300 

μg/l for the 24 hr LC50 and 190 μg/l for the 96 hr LC50. Therefore, NP will not have chronic effects 

on rainbow trout, having a 24 hr/96 hr value of 1.6 (Dwyer et al. 1995 as cited in EPA 1996). The 

LC50 for all fish for NP9E ranges from 1,300 – 1,000,000 μg/l (1.3 – 1,000 ppm). The concern 

concentration of NP for rainbow trout is 3 μg/l. This is also the concentration of the No Observable 

Effect Concentration (NOEC). 

In a nationwide 30-river study done by a panel of manufacturers under EPA’s recommendation, no 

concern concentrations for pelagic organisms were exceeded with any of the measured 

concentrations. The highest measured concentration was 0.64 μg/l of NP, which came from the 

highly polluted Grand Calumet River in Indiana. From this study it was determined that nationwide, 

there appears to be a low risk posed by NP to pelagic organisms. 

Toxicity of NP9E, the ingredient in R-11®, is 1-2 orders of magnitude less than NP, while toxicity of 

the intermediate breakdown products, NPEC and shorter chain NPEs, are intermediate between NP 

and NPE (EPA 1996). Bioconcentration of NP in freshwater fish appears to be low to moderate 

(EPA 1996). 

It is assumed insignificant effects will occur as a result of using the R-11® surfactant. This is due to 

NP9E being less potent than NP by an order of magnitude in estrogenic effects, the short half-life 

(few to several days), it is adsorptive to stream sediments and solid organic carbon, and heavily 

polluted rivers were under the concern concentration of NP for rainbow trout. In addition, this is a 

single plant spray operation, few plants near the stream are expected, and for those that are, special 

precautions are in place. 
44 SALMON RIVER Knapweed Environmental Assessment 

HI-LIGHTTM Blue Dye 

A colorant, Hi-LightTM manufactured by Becker-Underwood, will also be used to show the 

applicators where they have been. The Material Safety Data Sheet indicates there are no reportable 

quantities of hazardous ingredients present, and no toxic chemical(s) subject to reporting 

requirements. This colorant is short-lived, and breaks down in a matter of days. 

Alternative 2 

The manual technique of removing the knapweed will have negligible direct effects on the 

anadromous fish species of the Salmon River sub-basin. The manual technique would be 

implemented over a limited number of acres, reducing the physical disturbance to a negligible 

direct effect. 

Alternative 3 

The indirect and direct effects to aquatic species of the manual treatment portion of this 

alternative are the same as in Alternative 2 discussed above. The effects of the herbicide 

portion of this proposal would be the same for glyphosate, picloram, and clopyralid and 

additives as discussed Alternative 1. 

Alternative 4 

If no treatment of the knapweed were to occur, negative effects to the riparian vegetation would 

occur. It is well-documented that the knapweed takes over ecosystems in the intermountain west. 

With its capacity to inhibit other vegetation growth in its vicinity, no or little riparian vegetation 

would be able to compete or fill the interstitial bare areas of soil/cobble bar. Although the native 

riparian vegetation growing on the river bars has evolved within the current disturbance regime of 

high flows and scour, it cannot out-compete the knapweed. Because of this, riparian vegetation will 

decrease over time as it is out-competed by the knapweed. Direct effects would include a reduction 

in shade along the margins of the river, and a possible greater instability of the cobble bar 

margins. Cobble bars move as part of the river process; however, the root structure of the riparian 

vegetation does add some structure so that the banks can stand up to the lower flows and move at the 

higher flows. In addition, the riparian vegetation does add margin cover for newly emerging/hatching 

fish. Small branches that overhang into the margin water of the river provide excellent cover for the 

newly emerged/hatched fishes of the Salmon River. This cover is very important during this early 

life-stage of salmonids, providing cover from predators in a flow velocity that is conducive to their 

being able to maintain their station. The margin habitat is very important early on as the fish do not 

have the ability to swim in the faster intermediate and thalweg currents. Indirect effects of not 

treating knapweed may negatively affect fisheries if riparian habitat is degraded over time. 

Cumulative Effects may occur if additional habitat is degraded elsewhere in the watershed 

from spreading noxious weeds, fire, flooding, and other disturbances. 
SALMON RIVER Knapweed Environmental Assessment 45

Issue 3 - Effects To Non-Target Species Including Plants, 

Wildlife, Insects, Amphibians, Fungi, and Microorganisms. 

Environmental consequences relative to this issue will be discussed for each alternative. The 

discussion will also include effects to the target species, spotted and diffuse knapweeds. This section 

will include a discussion of general effects to potentially affected species, including those with special 

management status, i.e. federally listed and Forest Service Sensitive species and Survey and Manage 

Species (SM). Specific analysis of effects to TESP species are disclosed in the Biological 

Assessments and Evaluations prepared for the proposal and summarized in the discussion of effects 

to alternatives relative to Issue 4 below (TESP). This issue will be measured by risk of exposure and 

toxicity. 

Botanical Analysis 

Non-target plant species are all species of plants other than the target species, which include Klamath 

National Forest Sensitive and “Watch List” species, SM species, and other vascular plants, and 

microorganisms (bacteria, yeast and fungi) that may be affected by the project. Habitat does not 

occur within the project area for botanical SM or Watch List species and surveys are not required. 

Forest Service Sensitive species will be addressed in the Biological Evaluation for this project. The 

remaining non-target plants are addressed below. 

Wildlife Analysis 

Non-target wildlife species considered in the analysis include SM amphibians and mollusks, as well 

as TESP species. In addition, consideration was given to representative species selected from lists 

developed in the LRMP. Many of the species listed are not present within the vicinity of the project 

area during the time of proposed treatment. Additionally, the habitat types represented (river bar, 

roadside, and upland plantations) and the total areas (15 acres) involved in treatment comprise a very 

small percentage (less than 0.0001%) of the total landscape utilized by wildlife species in the Salmon 

River Watershed. 

No adverse effects to the two Federally listed bird species (northern spotted owl and bald eagle; 

peregrine falcons are delisted) are anticipated as a result of the project as the probability of occurrence 

or risk of exposure in the area is low to non-existent (Wildlife Biological Assessment). Habitat for 

SM species of concern, Del Norte salamander, and several mollusk species does not occur within 

sites proposed for treatment, therefore no surveys are required. 

Few of the species considered in the analysis are expected to be present in the areas proposed for 

treatment. The most likely species to be present and potentially affected by the project are black bear, 

blacktailed deer, pallid bat, Townsend’s big-eared bat, western pond turtle, and foothill yellow legged 

frog. Potentially, but less likely, willow flycatcher could occur as well. The analysis will focus on 

potential effects to these species. 

Any potential effects from the proposed or modified proposed action would be indirect through 

the ingestion of sprayed vegetation or secondary effects from consuming prey that had ingested 

or been sprayed with herbicide. There are no direct or cumulative effects to wildlife. The 

anticipated risk of exposure and the level of toxicity available to wildlife are very low. 
46 SALMON RIVER Knapweed Environmental Assessment 

Alternative 1 

Botanical Effects 

The direct effects on target and non-target plant species in the Proposed Action will come from the 

use of herbicides to treat the target plants, and from follow up treatment which will include various 

manual methods of removal. Both methods of treatment are expected to have short-term impacts 

within a very limited area. Four factors determine plant responses to use of chemicals: chemical type, 

rate, frequency, and method of application. Low rates will generally have less effect on most plants. 

More frequent and higher rates of applications would be expected to have greater effects. Use of 

backpack sprayers will selectively treat plants and minimize exposure to non-target species. Literature 

indicates (Rice et al, 1997; Sheley, 1999) re-treatments of herbicides within five years would be 

necessary to achieve eradication. 

Direct effects of glyphosate (RodeoTM) on non-target plants and microorganisms, are expected 

to be slight, with no indirect effects. Some broad-leaved non-target species, if present in close 

proximity to target plants may be affected more with the combination of 2,4-D and glyphosate 

than with glyphosate (RodeoTM) alone. Picloram and clopyralid effects on non-target plants and 

microorganisms are expected to be slight to none. Effects to target species are expected to be 

highest in this alternative due to the application of herbicides on all sites. 

Glyphosate (RodeoTM) 

Glyphosate (RodeoTM) is in the class of herbicides that inhibit amino acid synthesis. It is taken up 

rapidly by leaves, and not at all by roots due to its binding properties in the soil. Ultra-violet light and 

soil microorganisms break down glyphosate (RodeoTM) in 3 to 130 days (Info. Ventures, Pesticide 

Fact Sheets). Plants cannot uptake glyphosate (RodeoTM) from the soil because it binds tightly to the 

soil, and is not available in solution once contact with the soil has been made. The only route of 

exposure to plants is through direct contact. Glyphosate (RodeoTM) is a non-selective herbicide. 

Most plants that come in contact with it are killed or damaged, depending on the rate and timing of 

application. Residues of glyphosate (RodeoTM) on selected plant species can be detected in small 

amounts for up to 36 weeks after treatment (Segawa, 1998); however, these residues on dead and/or 

decaying plant material are not dislodgeable residues, and cannot re-enter the system via water (S. 

Thornhill, SCDA, personal communication, 2000).

Glyphosate (RodeoTM) is not the most widely used herbicide to treat knapweed because: 1) it is nonselective, 2) it has a limited time-frame during which it is effective, and 3) it has no residual effect on 

the seed bank necessitating annual treatments of seedlings. However, it is proposed for use in the 

riparian area because of its low ecological risks. Glyphosate (RodeoTM) has an excellent rating for 

effectiveness on spotted knapweed if used on seedlings, rosettes, and leafy re-sprouts as proposed 

(BLM, 1985). 

Non-target plants on the river bar consist of non-native annual grasses, perennial native grasses, 

sedges, scattered conifers and alders, willow, big-leaf maple, cottonwoods, non-native blackberries, 

and forbs. Where the knapweed is growing among other vegetation, particularly dense grass and 

forbs, some loss of non-target vegetation is expected from the use of glyphosate (RodeoTM). 

Application on mid-season germinants, re-sprouts, and/or missed juveniles from earlier applications, 
SALMON RIVER Knapweed Environmental Assessment 47

after most grasses have gone dormant for the season, will limit the effect on grasses. Since plants do 

not uptake glyphosate (RodeoTM) from the soil, it is not possible for vegetative blackberry bushes to 

accumulate the chemical in the fruit. Aquatic plants can only be affected by glyphosate (RodeoTM) if 

the above water portions come into contact with it. There are no aquatic plants that would be affected 

in the project area. Most algae are unaffected by glyphosate (RodeoTM) (SERA, 1996). Direct 

effects of glyphosate (RodeoTM) on non-target plants are expected to be slight, with no indirect 

effects. 

There are a number of studies on the effects of glyphosate (RodeoTM) and microorganisms. Some 

laboratory studies show that there is some short-term decrease in some microorganisms associated 

with the use of glyphosate at various dosages (SERA, Appendix 2-2, 1996). Direct effects on 

microorganisms from the use of glyphosate (RodeoTM) in the field are expected to be slight to 

none, with no indirect effects. 

Glyphosate (RodeoTM) + 2,4-D (WeedarTM) – The addition of the amine formulation of 2,4-D to 

glyphosate (RodeoTM) enhances the foliar action of the glyphosate (RodeoTM) on broadleaved species. 

Effects on non-target plants would be equal to that of glyphosate (RodeoTM), as it is a non-selective 

chemical, and the addition of 2,4-D to the mix does not negate that property. Some broad-leaved 

non-target species, if present in close proximity to target plants may be affected more than with 

glyphosate (RodeoTM) alone. 

2,4 – D (WeedarTM and WeedoneTM) 

2,4–D (WeedarTM and WeedoneTM) is in the class of growth regulating herbicides that affect 

broadleaf plants through a multitude of physiological processes. Uptake is primarily from leaf 

surfaces, and briefly from the roots. 2,4-D is rapidly (one month) degraded in the soil by 

microorganisms and has no residual effect on plants. The one formulation (WeedarTM) is an amine 

formula, low in volatility. It is formulated for use in or near water. This formulation would be 

combined with glyphosate (RodeoTM) for added efficacy. 

The ester formula (WeedoneTM) is proposed for use in combination with other chemicals to enhance 

efficacy through increased foliar uptake in the upland areas away from water. Discussion of effects of 

2,4-D in combination with glyphosate (RodeoTM), clopyralid (TranslineTM), or picloram (Tordon 

22KTM) will be discussed in the analysis of those chemicals. 

Picloram (Tordon 22KTM) 

Tordon 22KTM (picloram) is the most effective herbicide for control of knapweeds, and provides 

excellent (nearly 100%) control of both species of knapweed at low rates for two years or more 

(Sheley, 1999). 

Picloram (Tordon 22KTM) is in the class of growth regulating herbicides that are selective to broadleaf 

plants. It has a residual soil activity for two to three years depending on the rate of application, soil 

conditions, and weather. 

Effects to non-target plants from picloram (Tordon 22KTM) will vary depending on situational 

variability (soil, climate, slope), off-site movement, and/or direct contact. Of all the herbicides 

analyzed for this project, picloram (Tordon 22KTM) has the highest potential to affect non-target 
48 SALMON RIVER Knapweed Environmental Assessment 

broadleaf vegetation, for a period of approximately two years (Rice et. al.). The sites proposed for 

picloram (Tordon 22KTM) treatment have a very dense cover of knapweed that has already outcompeted the native vegetation. The effects on the minor amounts of other broad-leaved species 

present due to picloram (Tordon 22KTM) will be slight. The most advantageous effect of 

picloram (Tordon 22KTM) on non-target vegetation is the increase in grass cover in direct 

relation to the decrease in knapweed cover (Rice, 1998). 

Picloram (Tordon 22KTM) has very low toxicity to microorganisms at up to 1,000 ppm in laboratory 

studies (USDA, Rogue River NF, 1999). Most herbicides are broken down by microbial action in the 

soil, the rate at which is governed by population levels. The sites proposed for treatment with 

picloram (Tordon 22KTM) vary in levels of organic matter and hence the levels of microorganisms 

that usually occupy that layer in the soil. Effects on microorganisms in the field application of 

picloram (Tordon 22KTM) are expected to be slight to none (SERA, 1999). 

Clopyralid (TranslineTM) 

Clopyralid (TranslineTM) is in the class of growth regulating herbicides that act as a synthetic 

hormone, altering the plant’s metabolism and growth characteristics, ultimately affecting the plant’s 

ability to transport nutrients. It is relatively non-toxic to grasses and some broadleaf plants. 

TranslineTM provides nearly 100% control of spotted knapweed for about two to three years when 

applied before flowering and longer if applied at the rosette stage (Rice, et al., 1997). Clopyralid 

(TranslineTM) is also effective for treatment of diffuse knapweed, and may also require multiple 

treatments in subsequent years to be most effective. 

Effects to non-target plants will result from unintended direct deposition, or spray drift. Since 

clopyralid (TranslineTM) is selective, most species of grasses, conifers, and other trees and shrubs will 

not be affected by direct application or drift. For broadleaf plants directly sprayed, effects will vary 

with the timing of exposure. The sites proposed for treatment with clopyralid (TranslineTM) are the 

same sites as addressed in the picloram (Tordon 22KTM) discussion above. The same conclusion 

applies: the direct effect to non-target broadleaf plants is expected to be slight, due to the low 

levels present on the sites now. As knapweed cover decreases, grass cover is expected to increase. 

Clopyralid (TranslineTM), at concentrations of 1-10 ppm in soil, had no effect on decomposition 

(hence microorganisms) or spore germination (SERA, 1999). 

Clopyralid (TranslineTM) + 2,4-D 

The combination of these two chemicals create different effects on both target and non-target plants. 

Data indicates that for spotted knapweed, early applications (at bolt and bud stages) of the mix had 

slight additional benefits to knapweed control than the clopyralid (TranslineTM) alone (Rice et al, 

1997). At later stages, the combination was less effective. There is no data with regard to treatment 

of diffuse knapweed with this combination. 

Early application of this combination can have a greater effect on non-target plants than with 

clopyralid (TranslineTM) alone, if they are present on the site. A decrease in non-target forbs 

can be expected, for approximately one year. Later applications have no effect on abundance 

or richness of most non-target forbs (Rice and Toney, 1998). 
SALMON RIVER Knapweed Environmental Assessment 49

Wildlife Effects 

Potential effects of implementing the alternatives to wildlife include: (1) direct toxic effects on 

growth, health, behavior, or reproduction; physical injury; or death from consumption of an herbicide; 

(2) a secondary toxic effect due to the consumption of a prey which has had direct consumption of an 

herbicide; (3) effects on wildlife species habitat due to vegetative changes; and (4) disturbance to 

wildlife from the eradication activity. Under Alternative 1 direct and indirect effects to wildlife 

from the use of glyphosate are expected to be minimal. Effects from use of 2,4-D in 

combination are variable among species ranging from slight to moderate. Use of clopyralid and 

picloram in the uplands poses a very low risk to wildlife species in the project areas.

The Region 5 FEIS (USDA, 1988) analyzed the effects of 2,4-D, glyphosate (RodeoTM), and picloram 

(Tordon 22KTM) on wildlife. Information on the effects of clopyralid (TranslineTM) is included in the 

SERA Risk Assessment (SERA, 1999). Numerous studies are cited in these and other documents 

that indicate there is little direct danger to wildlife when chemicals are applied at the recommended 

rates. When herbicide doses exceed 1/5th of the LD50 values, most wildlife species are considered to 

be at risk of mortality or lesser toxic effects. The proposed rates are also well below the 1/5th LD50

criterion. Expected doses from this alternative are up to 100 times lower than the laboratory test 

levels that demonstrate acute or chronic toxicity. 

Research has shown that wildlife are not at risk from label recommended herbicide doses, particularly 

when they consume only a portion of their diet as contaminated food items. A few species, 

particularly small birds and mammals, were found to be at risk under worst-case conditions, where 

animals were directly sprayed (dermal effects) and consumed only contaminated food items (ingested 

effects). Direct spraying of individual animals would not likely occur with hand spraying. Wildlife 

will move away or seek cover from the activity. The potential for consuming contaminated 

vegetation as a part of their diet would be negligible for most wildlife species, with the possible 

exception of small rodents living on site. 

Of the species of concern, the foothill yellow legged frog, the Western pond turtle, and willow 

flycatcher could be present in the river bar portions of the project area. A suitable buffer from the 

edge of the water will minimize potential exposure to spray. Spray will not be applied to, or allowed 

to drift onto, any water surface. Both frogs and turtles forage in the water, so they would not be 

directly ingesting herbicide. Flycatchers are insectivorous and do not consume vegetation. Indirect 

exposure to herbicide could occur through ingestion of prey species, wasps, bees, moths, caterpillars, 

flies, and grasshoppers. 

Townsend’s big-eared bat and the pallid bat are carnivorous. They could also be potentially indirectly 

exposed to herbicides through prey species. Because the herbicide chemicals are not stored in plant 

tissue or body tissue, doses received via the food chain are expected to be negligible. 

Black bear and blacktailed deer are both habitat generalists and do use river bars and are commonly 

seen along roadways and in plantations. It is not expected that they would utilize the target vegetation 

being sprayed. 
50 SALMON RIVER Knapweed Environmental Assessment 

Glyphosate (RodeoTM) 

Glyphosate (RodeoTM) does not bioaccumulate; there is rapid elimination of the residues and it is 

not retained in the tissues of mammals, birds, and fish (Risk Assessments Region 1,2,3,5, etc. 1992, 

SERA 1996, and Info. Ventures 1999). Research on mammals has shown that very high doses of 

chemical are needed to cause acute oral toxicity. The LD50 for rats is 4320 mg/kg/day of body weight 

and 3800 mg/kg/day for rabbits. Levels greater than 2000 mg/kg/day are considered to be practically 

non-toxic (RAs, 1992, 1996). 

Potential effects of glyphosate (RodeoTM) on the riparian related species, pond turtle, yellow-legged 

frog and willow flycatcher are very low. The chemical is easily diluted, as well as easily adsorbed by 

the soil; the chemical half-life is very short and as such the risk to both frogs and turtles is quite low 

(Info. Ventures 1999). It is also non-toxic to aquatic invertebrates, a food item for these species. 

Research has shown this compound is practically non-toxic to birds (Info. Ventures). It is also 

practically non-toxic to bees, a common prey item for flycatchers, and other birds. Because the 

chemical does not bioaccumulate in tissue, there is little risk to Townsend’s big-eared bats or pallid 

bat. Any chemical residues present on insects consumed immediately after the herbicide treatment 

would be eliminated from their bodies. 

The surfactant, R-11®, will be used in conjunction with glyphosate (RodeoTM) to facilitate the 

adherence of the herbicide to the plant leaves. Research has shown R-11® can have effects on gilled, 

aquatic organisms (minnows and shrimp) in lab situations. However, at field spray concentrations, an 

accidental direct spray into a stream would be quickly diluted and have negligible effects (Bakke, 

1999). 

2,4-D 

There are significant differences in toxicity to vertebrates among the forms of 2,4-D. In many 

instances, the toxic response seems to be species-specific (RA, 1992). The amine formula is 

generally non-toxic to fish, while the ester form is highly toxic. Oral LD50’s in mammals ranges from 

100 mg/kg/day for dogs, cattle, and swine to 848 mg/kg/day for guinea pigs. In birds, acute oral LD50

values range from 472 mg/kg/day in pheasants to more than 2000 mg/kg/day in mallards. For both 

amine and ester forms, an LD50 of over 5000 was recorded for Japanese quail, bobwhite, and ringnecked pheasant. No reproductive or teratogenic effects were observed in chickens, and pheasant 

eggs when sprayed with various forms of 2,4-D, even at dosage levels of up to 20 times the field 

application rate. Based on studies with honey bees, insects appear to be relatively tolerant to high 

levels of 2,4-D. 

The bioaccumulation ratio is low for test animals exposed to 2,4-D and accumulated residues are 

rapidly excreted after exposure (RA, 1992). Studies have found low levels of residue ranging from 

0.05 to 6 mg/kg in live and kidney tissue samples from wildlife, including deer, pheasant, grouse, and 

others.

The amine formula dissolves readily in water so concentrations are diluted quickly and since 

streamside buffers would be used, herbicide could only enter the water accidentally. Aquatic 

invertebrates (Daphnia) have a low LC50, but due to the very low concentrations and brief time the 
SALMON RIVER Knapweed Environmental Assessment 51

chemical may be in the water, there would be little effect on the abundance of prey base for frogs and 

turtles (Norris, et.al., 1991). 

In the case of willow flycatcher, pallid and Townsend’s big-eared bats, and black bear the risk of 

secondary effects from consumption of exposed prey is low due to the fact that 2,4-D doesn’t 

bioaccumulate. 

Effects to deer are expected to be minimal. Although deer will move through the treated sites, they 

do not represent preferred forage habitat for deer. A deer would have to concentrate on sprayed sites 

exclusively for some time in order to consume high enough doses of herbicide to cause harmful 

effects. This is not the normal foraging pattern for deer, as they are continually moving as the 

browse. 

The surfactant, R-11®, would also be used with 2,4-D. This product should not have any effects on 

animals using upland sites where the spray would be used (Bakke, 1999). 

2,4-D is variable in its effects on individual species dependent on the form of the chemical 

making it difficult to generalize about the effects to wildlife. The risk of potential carcinogenic 

effects from exposure has not been demonstrated by research studies (SERA, 1997) 

Clopyralid (TranslineTM) 

Toxicity studies of clopyralid (TranslineTM) have been conducted on laboratory mammals, specifically 

rats, mice, rabbits, and dogs. The acute toxicity is quite low, with an LD50 of 3000 mg/kg/day to 

greater than 5000 kg/mg/day depending on process used to produce it (SERA, 1999). 

The chemical may be more toxic to birds than mammals, although studies are limited. The results of 

one study on mallards determined an LD50 of 1465. A problem with all the studies on birds was that 

none of the exposures resulted in mortality high enough to estimate the LD50 (SERA, 1999). 

Tests of chronic toxicity show no carcinogenic effects. There was no evidence of cancerous tumors 

in a two-year feeding with rats at 2000 mg/kg/day of a two-year feeding of mice at 1500 mg/kg. 

Likewise, studies showed no effects on reproduction, fetus development, or mutation in a variety of 

animals. The metabolism of clopyralid has been studied in one mammalian species. It suggests that 

clopyralid does not bioaccumulate in rats in detectable amounts, and that 79-96% of the dose is 

excreted unchanged in the urine during the first 24 hours (SERA, 1999). Secondary effects would be 

negligible for this chemical. 

Research indicates this chemical is a low risk to wildlife when used at the recommended levels 

(SERA, 1999). There is little risk of acute and chronic effects, and indications are it does not 

bioaccumulate in the body so secondary effects are not an issue. The small size and number of 

the plots to be treated and their wide distribution would further reduce any adverse effects to 

wildlife. 

Picloram (Tordon 22KTM) 
52 SALMON RIVER Knapweed Environmental Assessment 

Picloram (Tordon 22KTM) will be used in the upland sites away from riparian habitat. Effects to 

turtles, frogs, and willow flycatcher are not of concern with use of this chemical in these areas as 

there is no habitat for these species where this chemical is proposed for use. The total acreage to be 

treated is with picloram is approximately one acre. Sites will be treated using a combination of 

picloram and 2,4-D in this alternative. 

Research indicates that this herbicide is relatively safe in the environment. Because of its persistence 

in the soil (half-life of 20-300 days) it is available in the environment longer than the other chemicals 

to be used in this alternative (Info. Venture and Extoxnet). Picloram (Tordon 22KTM) is rapidly 

absorbed through the intestinal track of animals and excreted unchanged in the urine (SERA, 1999). 

Therefore, secondary effects to wildlife are expected to be minimal. 

Studies conducted on birds indicate that picloram is practically non-toxic (U.S. EPA 1995). The 

LD50s are from 2000 to 5000 mg/kg/day in ducks, pheasants and quail, with no mortality observed 

even at the highest levels (EXTOXNET 1999). Test results indicate that the chemical is slightly to 

non-toxic in mammals, with greater toxicity observed in large animals (i.e. cattle >720 mg/kg/day). 

Smaller mammals, such as rats, have an LD50 between 5000 and 8200, 2000 to 4000 for mice, and 

approximately 2000 for rabbits. 

There is some evidence that at high concentrations, picloram (Tordon 22kTM) in combination with 

2,4-D esters may have an additive (not synergistic) effect, the manner in which picloram (Tordon 

22kTM) and 2,4-D are rapidly excreted in an unchanged form by mammals, reduces the risk of 

interaction with other molecules (U.S. EPA, 1995). 

Picloram (Tordon 22kTM) is relatively non-toxic to insects based on studies conducted on honey bees. 

The chemical has shown no effect on reproduction, no increase in birth defects. There is no evidence 

of cancer and mutations associated with picloram (Tordon 22kTM) (Risk Assessment 1992, SERA 

1999). 

The limited use of picloram (Tordon 22kTM) in this alternative presents a low risk to the 

potentially affected wildlife species in the project area. 

Alternative 2 

Botanical Effects 

This alternative would utilize manual/mechanical methods for treatment of target plants, including 

hand pulling, mulching, mowing, and propane torching. The sustained effort and number of 

workers required to eradicate knapweed on the total infested acreage in the Salmon River must 

be carried out multiple times every year for approximately 12 years, or until viability of seed in 

the seed bank is exhausted, in order to achieve objectives. Literature and experience indicate 

that the sustained effort required to achieve eradication using mechanical means is difficult to 

achieve. 
SALMON RIVER Knapweed Environmental Assessment 53

Effects from hand pulling on target plants will vary by site conditions (size, soil type, moisture level, 

etc.). Small, roadside populations can be eliminated by hand pulling, and returning seedlings, if small 

in number, can also be treated effectively by that method. Most of the larger river bar sites are 

covered with rocks varying in size from small and medium sized cobbles to large boulders. The 

knapweed roots can often be twined down between rocks. Moving the rocks necessary to remove 

enough of the roots to prevent re-sprouting creates bare ground, and this disturbance creates the 

perfect medium for seedling germination. Knapweed will re-sprout if the plants are not cut below the 

crown at least two inches (Sheley, 1999). Hand pulling also increases the amount of seed available 

for germination. The action of pulling up the plants and roots brings seeds that may otherwise be 

buried to the surface, where germination then occurs. Seed viability decreases with time; thus each 

successive year that seeds remain undisturbed and do not germinate, the viability and germination 

potential decreases (Orloff, personal communication, 2000). Encouraging seeds to germinate allows 

an increase of propagative plant material to enter the environment (i.e. broken tap-root fragments, 

root hairs, etc.). As the amount of propagative material present increases, the population density may 

also increase, resulting in a lower probability of eradication and lower efficacy of the method. 

Technical bulletins out of the States of North Dakota and Montana (MSU Circular 311, May 1998; 

and NDSU, W-1146, March 1998) do not consider hand pulling an effective option for control or 

eradication on large, densely infested knapweed sites. 

Hand pulling the large, densely infested sites would create substantial disturbance and generate bare 

ground, which then would be susceptible to being replaced with knapweed seedlings. This could 

occur within the same growing season if hand pulling is conducted early in the year when moisture is 

plentiful. The site conditions have a large effect on whether or not hand pulling can be successful or 

not. In areas of large rocks or heavy clay soils, it would be difficult to remove enough of the root to 

avoid re-sprouting, even under moist conditions. Smaller plants that have less extensive root systems 

would break off right at the root crown, making re-sprouting highly probable. On lighter soils where 

removal of the entire plant is possible, there would be a germination flush of seedlings due to 

disturbance. Non-target plants in close proximity to knapweed will most likely also be pulled up 

when knapweed is pulled up. This will eliminate competition on the sites of desirable species to 

compete with the knapweed. The increased frequency of visits to infested sites to hand pull plants 

will increase the risk of spread by humans picking up seed lodged in soil in boots and on tools, and 

when handling and transporting flowering and/or seeded material for disposal. 

Hand pulling diffuse knapweed in anything but the rosette stage is very different than spotted 

knapweed. The plant is significantly prickly, much more branched and voluminous for removal, and 

if flowers have been pollinated, the plants will continue to develop ripe seeds after removal from the 

soil (Roche, and Roche, 1990, in Sheley, 1999). Thus all plant material must be disposed of. 

Effects to microorganisms from hand pulling are likely to be low. Soil compaction from 

repeated passes over certain areas for treatment would occur within infested sites and this may 

affect the relative abundance of species to favor those species of microorganisms better adapted 

to compaction. 

Mulching with plastic: The basic premises of using synthetic materials for mulching is the 

solarization of the soil to the point where the vegetation under the cover is killed, prevented from 

germinating, or otherwise suppressed from growing; and as barriers for weed control. There has been 

much research on the efficacy of available materials. The variables considered include the color of 
54 SALMON RIVER Knapweed Environmental Assessment 

the plastic, the thickness of the material, and the chemical make-up of the plastic (FAO, 1991). The 

soil under clear plastic generally gets hotter than under black plastic if applied totally flat against the 

ground; however, the difference in temperature was found to be insignificant in the effects on target 

weeds in one study (FAO, 1991) and significant in temperature differences, but still ineffective on 

perennials in another study (Horowitz, 1983). Most of the research on this topic comes from the 

agricultural applications of solarization under very controlled conditions, i.e. formed planting beds, 

bare flat soil, application of water under the mulches, etc., and is focused on weed seeds, not 

established plants. There is limited information available on the application of these techniques in a 

wildland situation. 

From the literature, however, it is clear that: 

1. The materials used as mulch need to be laid as close to the ground as possible with no air gaps, 

in areas that have optimum solar radiation; 

2. The soil should be wet for maximum heating; 

3. Some weeds are more susceptible than others (mostly winter annuals; established perennials in 

some trials were not affected at all, (M. Horowitz, 1983); and 

4. The effects on different weed species will vary in duration. 

One of the drawbacks in using plastic mulches for control is the solid waste disposal of the material 

once it becomes unusable, and the cumbersome and expensive nature of its application. 

Effects on Target Plants

Based on trials with black plastic mulch in 1998, approximately 14,000 square feet at Kelly Gulch 

were mulched in 1999. For a variety of reasons, the large-scale mulching varied in effectiveness on 

the target plants. When the plastic was removed in the fall of 1999, some established knapweed 

plants appeared wilted and chlorotic, but still alive in some areas. Those plants have the potential to 

recover. Other mulched areas were apparantly more successful at killing and/or suppressing 

establised knapweed plants. Mulching has limited application for sucessfully meeting eradication 

objectives. It would not be practical for large scale treatment on all sites.

Effects on Non-Target Plants

Since mulching is a non-selective technique, it has the ability to affect all non-target plants under the 

plastic covers. Effects would vary by species. Some may be killed, some may just be suppressed, 

and others may be enhanced. Mulching studies under conditions similar to Salmon River have not 

been conducted and information is limited in the scientific literature. In the mulching trials 

conducted in 1998, one native forb appeared suppressed only, and some of the annual non-native 

grasses were also suppressed. 

The effects of mulching on fungi and microorganisms vary by species. Some fungi are eliminated 

if temperatures get hot enough; some fungi are enhanced (Abu-Gharbieh, in FAO, 1991). 

Microorganisms are reduced in the short-term, but are expected to recover in the long-term. 

Mowing is not considered an eradication or control method, but can be used to reduce seed 

production. It has been proven effective in combination with other methods (i.e.herbicides) (Brown et 

al 1996). Trials with diffuse knapweed resulted in 22% of plants mowed to a height of two inches 

each month of the growing season (April-October) still growing four years later (Roche and Roche, 
SALMON RIVER Knapweed Environmental Assessment 55

1990). Mowing in early flowering did not eliminate the production of viable seed for the year. 

Mowed spotted knapweed also continues to produce flowering stalks well into the late part of the 

growing season. It would have limited effectiveness alone or in combination with other mechanical 

methods. 

Propane torching can be effective on small knapweed seedlings, early in the year, before tap-roots 

have developed and fire season has begun. Torching will also have similar lethal effects on nontarget seedlings that come into contact with the flames. It is not likely that torching would have 

detrimental effects on fungi and microorganisms, as the duration of the flaming is usually shortterm. 

Wildlife Effects 

Direct effects discussed relative to herbicide toxicity will not occur in this alternative. Effects to 

wildlife in this alternative are expected to be minimal. 

Implementation of this alternative will result in more potential human disturbance to wildlife because 

of the greater frequency of treatment necessary to achieve objectives. Human activity may affect 

wildlife use of an area while the manual treatment is taking place; however, the amount of 

disturbance will be localized and short-term. Wildlife will only be temporarily disturbed. 

Alternative 3 

Botanical Effects 

This alternative will treat all areas using manual methods described in Alternative 2 as long as 

evaluation criteria are being met on all sites. If objectives are not met on any given site, herbicides 

could be used as described in Alternative 1. 2,4-D will not be used on any sites. Direct effects of 

chemical treatment on target and non-target plants in this alternative have been discussed 

above in Alternative 1. Effects under this alternative will be slightly reduced from Alternative 

1 due to the elimination of 2,4-D used in combination with glyphosate (RodeoTM) and clopyralid 

(TranslineTM) or picloram (Tordon 22kTM). It is expected that the overall efficacy of treatment 

will be slightly reduced (S.Thornhill, 1999). Some broadleaved non-target species will not be 

affected as much in this alternative due to the absence of 2.4-D. 

As described above, effects from hand pulling on target plants will vary by site conditions (size, soil 

type, moisture level, etc.). The discussion of effects of manual treatment in Alternative 2 above 

applies to this alternative. 

Observations on hand pulling efforts to date lead to the conclusion that: 1) re-sprouting necessitates 

the re-treatment of the same plants numerous times; 2) numbers of plants actually increase due to the 

disturbance that stimulates seed germination; and 3) preventing flowering by hand pulling bolted 

plants can work as a short-term control method, but is not adequate for eradication (W. Stephans, 

2000; and personal communication M. Knight, 1998, 1999). 

The hand pulling effects of this alternative on target plants will differ from those discussed in 

Alternative 2 primarily by the length of time anticipated to meet the objective of eradication. Hand 

pulling will take a longer period of time to achieve. In this alternative, if handpulling is successful at 
56 SALMON RIVER Knapweed Environmental Assessment 

meeting the objective of eradication, it is anticipated that eradication will be achieved in 10 years. If 

objectives are not met, herbicides will be used and the objective will be met within 5 years from the 

time the objectives are not met and herbicide use commences. This will result in a one to 10 year 

increase in the amount of time it would take to meet the objective in Alternative 1, which proposes 

herbicide treatment immediately. 
SALMON RIVER Knapweed Environmental Assessment 57

Wildlife Effects 

In this alternative, chemical herbicides will potentially be used as described in Alternative 1. 

2,4-D will not be used. Effects to wildlife will be reduced slightly less without the use of 2,4-D. 

The effects of this chemical are highly variable, ranging from non-toxic to highly toxic 

depending on the chemical form and which wildlife species is being considered. 

The effects of the manual treatment proposed for this alternative are the same as those 

described above in Alternative 2. 

Alternative 4 

Botanical Effects 

No action toward the eradication of knapweed will result in serious negative effects to 

biological diversity and critical ecosytem structure, organization and function in the Salmon 

River and adjacent areas at risk of infestation. 

The consequences of not controlling aggressive plant pests, knapweeds specifically, is welldocumented in the literature (see Appendix F), and known first hand in the intermountain region of 

the United States where spotted knapweed has infested more than 4.5 million acres (MSU, 1998). 

Spotted knapweed alters the structure, organization, and function of ecological systems (Sheley, 

1999; Harmful NIS, 1993). Effects of the No Action Alternative on ecosystem structure will include: 

1. Altering soil properties such as nutrient levels, organic matter content; decompostion rates, and 

rates of erosion; 

2. Altering composition of plant communities, by displacing native plant species and leading to the 

threat of extinction of rare plant elements. In 22% of the Federally listed Threatened and 

Endangered plants, noxious weeds either are the major cause of listing, or contribute to the 

reasons for listing (Harmful NIS, 1993). Biological diversity is impaired by invasive species 

causing population declines, species extinction, or simplification of ecosystems; and 

3. Altering the structure of animal communities and reducing habitat for insects, birds, or other 

organisms that are dependent on plant communities for forage, cover, and shelter. Effects on just 

one pivotal species of an ecosystem can cause major effects that cascade through the system like 

dominos. 

Effects of Alternative 4 on ecosystem organization will include: the reduction of soil microflora, the 

reduction of relative abundance of native plant species, allelopathy (the effect of one plant on 

germination and seedling establishment of another) where spotted knapweed inhibits other plant 

species and hence establishes pure stands, and long-term weed success due to seed production and 

viability. 

Effects of no action on the functions of ecosystems will include: altering soil moisture regimes, 

nutrient availability and cycling, reducing water infiltration rates and increasing runoff rates, and 

altering disturbance cycles. 

Most of the damaging effects to ecosystems are exemplified in the intermountain region where 

spotted knapweed dominates vast areas of wildland. The Salmon River watershed is a forested 
58 SALMON RIVER Knapweed Environmental Assessment 

ecosystem with a history of high interval disturbance regimes such as fires and floods. A similar trend 

of infestation could occur in that these conditions greatly increase the potential for knapweed to 

spread throughout the watershed and into other areas in Siskiyou County and adjacent areas. 

Wildlife Effects 

Effects of not treating knapweed and allowing it to continue to spread will have a long-term indirect 

negative effect on wildlife and their habitat. The subsequent reduction in biological diversity of 

plants could affect quantity and quality of forage for a variety of species. Encroachment of knapweed 

into early successional habitat areas will reduce the quality and quantity of forage, and potentially 

hamper the growth process of oaks for those species dependent on that habitat. Knapweed does not 

provide forage or habitat value for wildlife. 

The effects of knapweed infestations on wildlife habitat can be demonstrated by what has occurred in 

western Montana. Elk use was reduced by 98% on range dominated by knapweed when compare to 

range dominated by bunchgrasses. It was predicted a loss of 220 elk annually in Montana because of 

infestations on winter range. 

Issue 4 - Effects to Federally Listed and Proposed and Forest 

Service Sensitive Species (TESP) 

Three separate Biological Assessments and Evaluations, for wildlife, fish, and plants, were prepared 

for this project. They are available for review and upon request at the Salmon River Ranger District 

Office. 

Many of the wildlife and plant TESP species will not be present at the project sites, for a number of 

reasons: the project is outside the species range, the species does not use the limited habitats involved 

in the project, the timing of the project is different than the time the species could potentially use the 

sites, the species has very large home ranges and will infrequently and briefly use the sites, or the 

behavior of the species is such that they will not use the sites involved. The following species meet 

one or more of the criteria listed above: bald eagle, Northern spotted owl, marbled murrelet, peregrine 

falcon, Northern goshawk, California wolverine, Pacific fisher, American marten, great gray owl, 

Cascade frog, Southern torrent salamander, and all 25 species of Endangered or Sensitive species of 

plants found on the Klamath National Forest. 

The Biological Assessment /Biological Evaluation for federally listed terrestrial wildlife and Forest 

Service Sensitive species determined there will be no effect on the listed species, bald eagles and 

Northern spotted owl; no effect on Sensitive species peregrine falcon, Northern goshawk, California 

wolverine, Pacific fisher, American marten, great gray owl, Cascade frog and Southern torrent 

salamander from implementing this project. Furthermore, the project may affect individuals, but is 

not likely to result in a trend toward federal listing or loss of viability for the pallid bat, 

Townsend’s big-eared bat, willow flycatcher, western pond turtle, and foothill yellow-legged frog. 

The determination of no effect for bald eagle and Northern spotted owl was discussed with the U.S. 
SALMON RIVER Knapweed Environmental Assessment 59

Fish and Wildlife Service (USFWS). The USFWS, Yreka Field Office concurs with this 

determination. 

The Biological Assessment prepared by the District fisheries biologist for Federally listed fish species 

made a tentative determination that implementation of the project may affect but is not likely 

adversely affect (MANLAA) the continued existence of the SONCC coho salmon or their Critical 

Habitat; MANLAA the continued existence of KMP steelhead. The project may affect individuals 

but is not likely to result in a trend toward listing of spring-run chinook salmon. A final Biological 

Assessment (BA) has not been agreed upon with the National Marine Fisheries Service (NMFS), but 

will be completed prior to a decision. 

The Biological Evaluation (BE) for Forest Service Sensitive plant species determined there will be no 

effect to Sensitive plants. 

Alternative 1 

Effects to TESP species from implementation of this alternative have been documented in the BAs 

and BEs. Effects to these species are within those analyzed under the Wildlife, Botanical, and 

Aquatic species consequences sections above and will not be repeated in this section. Effects are 

expected to be minimal for these species as most of them, with the exception of the aquatic 

species are not located within the project area. 

Alternative 2 

Direct effects of manual treatment of knapweed on TESP wildlife, botanical, and aquatic 

species will be none to slight under this alternative. 

Alternative 3 

Effects to TESP will be within those analyzed above under the Wildlife, Botanical, and Aquatic 

species consequences for Alternatives 1 and 3. Effects are expected to be minimal for these species 

as most of them, with the exception of the aquatic species are not located within the project 

area. 

Alternative 4 

The effects of no action to TESP species are largely covered in the discussions under Wildlife, 

Botanical and Aquatic consequences of Alternative 4 discussed above. With the exception of 

aquatic species habitat adjacent to proposed treatment areas along the river bar and floodplain, the 

majority of species do not occur within the project area. Old growth dependent species such as the 

Northern spotted owl are not likely to be directly affected if no action is taken to eradicate knapweed 

in the short-term. In the long term, if no action is taken to eliminate knapweed, biological diversity 

could be affected in all the ecosystem communities within the watershed. In the event of catastrophic 

flood or fire, habitat could be converted from native vegetation to a knapweed dominated system. 

Loss of a healthy functioning ecosystem that contains a diversity of habitat components will 

ultimately affect the abundance and distribution of TESP species. 
60 SALMON RIVER Knapweed Environmental Assessment 

Issue 5 - Effects To Local Community Well-Being and Quality Of 

Life 

Many local citizens expressed concern that their unique rural community environment and quality of 

life will be adversely affected by the use of chemical herbicides.

This issue will be measured by whether the alternative proposes to use chemical herbicides. 

Alternative 1 

Chemical herbicides will be used in this alternative, potentially on all infested sites if necessary. 

Many letters from the public indicated that the use of synthetic herbicide products of any kind in the 

environment will be objectionable to them. They believe that the Salmon River watershed is pristine 

and relatively free of any toxic substances and that use of chemical herbicides will negatively impact 

their rural community environment and quality of life. 

Yes, this alternative proposes the use of chemical herbicides; this alternative will negatively 

impact the local citizens’ expectations of a pristine, rural community environment and 

relatively “chemical-free” quality of life. 

Alternative 2 

This alternative is a community-based alternative that proposes to use alternatives to chemical 

herbicides to eradicate knapweed. This alternative will avoid use of any synthetic products (except 

for plastic mulch) and utilize manual methods of weed removal. This alternative is widely supported 

by the local community. This alternative will require a persistent and committed expenditure of 

human resources to diligently maintain a level of treatment in order to eradicate knapweed and 

prevent its return and further spread. 

Chemical substances will not be introduced into the Salmon River community for the purpose of 

noxious weed treatment. The Salmon River citizens’ expectations of a rural community environment 

that is relatively “chemical-free” will remain intact. 

No, this alternative will not negatively impact the local citizens’ expectations of a rural 

community environment and quality of life

Alternative 3 

This alternative proposes continued manual, non-chemical treatment of knapweed through 

cooperative participation. This alternative will pursue non-chemical treatment as long as evaluation 

criteria are met on all sites within the area. Herbicides would be used as a “last resort” to treat 

knapweed only after mechanical treatment methods have been depleted. This alternative responds to 

some members of the public who indicated they will support the use of chemical treatment “as a last 

resort,” only after it is proven that alternate methods cannot achieve the objective of eradication. 
SALMON RIVER Knapweed Environmental Assessment 61

This alternative may be acceptable to those members of the public who believe all other practicable 

means have been attempted and agree with the monitoring results if they determine herbicides must 

be employed. This alternative still will be objectionable to those who are opposed to the use of any 

chemical treatment in the watershed under any circumstances. They believe that the use of chemical 

herbicides will negatively impact their rural community environment and quality of life. 

This alternative will negatively impact the local citizens’ expectations of a rural community 

environment and quality of life if chemical herbicides are used as a last resort; it will not if 

manual methods are effective at achieving eradication. 

Alternative 4 

No action will be taken to treat the knapweed infestation in the Salmon River area. Chemical 

herbicides will not be used. The Salmon River watershed will remain relatively “chemical-free” 

within the value system of local citizens. 

Large-scale knapweed infestation may impact local property values. It may affect the ability of 

landowners to raise animals and crops if knapweed invades pasture and garden areas. Recreational 

experiences may be negatively impacted by large-scale infestations of knapweed due to the reduced 

aesthetic value to some people who believe that non-native weed infestations are unappealing. 

This alternative may impact community values and quality of life, but herbicides will not be 

used. 

Issue 6: Adverse Effects from the Use of 2,4-D: 

Particular concern was expressed over the use of 2,4-D. There is strong local opposition to the use of 

this chemical in the Salmon River watershed. Environmental effects of 2,4-D are discussed in 

Chapter 3, environmental consequences of Issues 1-4. This issue will be measured by whether the 

alternative uses 2,4-D. 

Alternative 1 

This alternative proposes the use of both the amine and ester formulations of 2,4-D in combination 

with other herbicide formulations to be used on most sites. This alternative will negatively affect 

those opposed to the use of 2,4-D. 

Alternative 2 

This alternative does not propose the use of 2,4-D alone or in combination with other herbicides. 

This alternative will not negatively affect those opposed to the use of 2,4-D. 

Alternative 3
62 SALMON RIVER Knapweed Environmental Assessment 

This alternative does not propose the use of 2,4-D or any other herbicides. This alternative will not 

negatively affect those opposed to the use of 2,4-D. 

Alternative 4 

This alternative does not propose the use of 2,4-D or any action at all. This alternative will not 

negatively affect those opposed to the use of 2,4-D. 

Issue 7: Chemical Herbicides Should Be Used as a Last Resort: 

Alternative 1 

This alternative proposes the use of chemicals. This alternative does not utilize chemicals as a last 

resort. This alternative does propose monitoring to determine the effectiveness of treatment as follow 

up. 

No, this alternative does not consider alternative approaches to herbicide use. Monitoring will 

be conducted to evaluate the effectiveness of treatment after implementation. 

Alternative 2 

This alternative does not propose the use of chemicals at any time. Chemicals would not be used as a 

last resort. On-going monitoring would be conducted to determine the effectiveness of treatment. 

No, this alternative does not use chemicals as a last resort but does consider an alternative 

approach to herbicide treatment. Monitoring will be conducted to evaluate the effectiveness of 

treatment during and after implementation. 

Alternative 3 

This alternative proposes the use of chemical herbicides as a last resort after alternative methods have 

been determined to not be the most effective method of treatment. This alternative proposes an 

evaluation strategy to determine effectiveness of treatment in meeting objectives. Evaluation criteria 

will be used to determine if chemical herbicide use is needed. 

Yes, this alternative considers alternative approaches to knapweed treatment and utilizes 

chemical herbicides as a last resort. Monitoring will be conducted to determine the 

effectiveness of the treatment. 

Alternative 4 

No action would be taken to treat knapweed in this alternative. 

No, this alternative will not consider alternative approaches to treatment or monitoring 

effectiveness. 
SALMON RIVER Knapweed Environmental Assessment 63

Achievement of Purpose and Need for Action 

This section will evaluate the alternatives in terms of achievement of the purpose and need stated in 

Chapter One. An efficacy rating will be applied to each alternative that rates the effectiveness of 

treatment measures in meeting the objective of eradication proposed in each alternative. Efficacy will 

be expressed in terms of the percentage of plants eliminated, 100% elimination is the goal of 

eradication. The amount of time (duration) estimated to achieve eradication is also taken into 

consideration in determining the effectiveness of treatment. The longer the duration to reach the 

objective, the greater the chances are that knapweed infestations will spread beyond the ability to 

control them and the lower the probability of success. 

The different alternatives for treating spotted and diffuse knapweed have varying levels of 

effectiveness for meeting the purpose and need for action (eradication of the species). Scientific 

literature on spotted and diffuse knapweed was reviewed to assess the most effective treatment 

methods (see Appendix F)). Weed Specialists from Siskiyou County and throughout Northern 

California were consulted (S.Orloff, J.DiTomaso, S.Thornhill personal communication), chemical 

treatment and manual control methods were researched in the literature, and professional judgment 

and field experience was used to validate the assumptions. Diffuse knapweed for purposes of this 

exercise was considered to be similar to spotted knapweed and the two species were rated together in 

this analysis. 

Alternative 1 

The proposed action has the highest potential to achieve the purpose and need due to the use of 

herbicides on all sites to treat knapweed. Herbicides are generally considered to be the most effective 

tools in treating spotted knapweed for a number of reasons: 

• Spraying the plants does not create the disturbance that manual treatments create. The 

disturbance of the soil and plant material stimulates seedling germination. Direct treatment of 

live plant material will kill the plant without creating disturbance that promotes growth. 

• Use of contact herbicides (glyphosate, 2,4-D) assures the plant is completely killed, as opposed to 

hand-pulling that has the potential to leave plant material (roots) that can resprout.

• Chemicals that have an effect on soil seed banks (picloram and TranslineTM) have an added 

effectiveness in that treatment may only have to be conducted every other year or longer. 

• Spotted knapweed is a relatively long-lived perennial. Plants can live up to 9 years. Killing 

plants by spraying eliminates having to re-treat the same plants repeatedly. Retreatment is 

necessary when mechanical methods result in: re-sprouting following hand pulling; or remulching 

from unsuccessful mulching of large, established plants that are resistant and difficult to 

eliminate; or mowing the same plants every year. 

• Numbers of treatments per year are generally less than with other methods as regrowth does not 

occur after plants are killed. 

• Costs of treatment are generally less than other methods due to the labor costs, and retreatment 

costs can be expected to decrease at a faster rate than with other labor intensive methods. 

Treatment Cost 
64 SALMON RIVER Knapweed Environmental Assessment 

Based on SCDA data, the estimated cost for herbicide treatment is approximately $300.00 per acre. 

In the Montana study (Brown et al 1999), the cost of chemical treatment per acre was approximately 

$30.00 per acre for 2 years. 

Based on the literature (Brown, et al. 1999) and professional opinion, this alternative is 

expected to achieve 100% effectiveness in eliminating knapweed populations within 5 years. 

Alternative 2 

This alternative has a low efficacy rating due to the use of only manual methods on all population 

sizes. Even though manual pulling is effective on small population sizes, the total acreage of small 

sized populations is small relative to the overall infestation. 

• Manual treatment requires complete removal of all plant material (esp. seeds and roots) from the 

site or re-growth will occur. 

• Manual pulling and digging encourages seed germination by creating bare ground through 

disturbance, bringing up seed that might otherwise stay buried (and lose viability) by churning the 

soil. 

• The increased number of visits to each site and the length of time involved in manual treatment 

increases the potential for spread by increase in human traffic through infested areas. 

• An adequate workforce for achieving eradication must be sustained at a higher level and over a 

longer period of time than that for chemical control. 

• Manual treatment is much more labor intensive and requires more person hours of labor, which 

contributes to a much higher cost of treatment for this alternative. 

Treatment Costs 

The cost of mechanical treatment is the highest of all the alternatives, estimated at approximately 

$15,000 per initial treatment per acre. In studies of methods used to control spotted knapweed in 

Montana, hand pulling bolted plants twice a year for two years produced 60% effectiveness at a cost 

of $13,900.00 per acre (the wage rate was $9/hour) (Brown et al., 1998). Using local data from the 

Kelly Gulch site, the Salmon River Restoration Council spent approximately 4 hours at $10/hr. to 

hand pull a 110 sq.ft. plot (.0026 acre) of densely infested knapweed (costs were $40 x 385 = 

$15,400/acre). Another plot of one tenth the density of the previous example took one hour to weed. 

Follow-up treatments would cost less, depending on return rate of the plants and subsequent 

germination from the soil seed bank, however multiple treatments are required per year. 

Based on the literature (Brown, et al. 1999), professional opinion, and experience to date, this 

alternative is expected to achieve 60% effectiveness and will eliminate knapweed populations 

within 10 to 12 years 

Alternative 3 

This alternative has a moderate efficacy rating because of the delayed use of the most effective 

treatment. The discussion of efficacy of treatment above in Alternatives 1 and 2 above applies to this 

Alternative. The efficacy rating is expressed as a range depending on the results of evaluation of the 

treatment. The overall efficacy rating is expected to decrease for the following reasons: 
SALMON RIVER Knapweed Environmental Assessment 65

• delayed use of the most effective method of treatment (herbicide use) if used at all. 

• this alternative does not include the use of 2,4-D in combination with RodeoTM, so is slightly less 

effective as described above in Botanical effects section. 
66 SALMON RIVER Knapweed Environmental Assessment 

Treatment Costs 

Treatment costs for this alternative will vary depending on whether mechanical or herbicide treatment 

is used and for what. The cost per acre would vary from $300.00 to $15,000. 

Based on the literature (Brown, et al. 1999), professional opinion, and experience to date, this 

alternative is expected to achieve 60-100% effectiveness and will eliminate knapweed 

populations within 5 to 10 years 

Alternative 4 

This alternative takes no action towards eradication of spotted knapweed and has no efficacy rating. 

Chapter 4

List of Preparers

Agencies and Persons Consulted

The following Forest Service specialists either participated on the Interdisciplinary Team or provided 

input to the analysis: 

Anne Yost Range Conservationist, ID Team Leader 

Marla Knight Botanist 

Brenda Olson Fisheries Biologist 

Jay Power Geologist 

Marc Williams Wildlife Biologist 

Candy Cook-Slette Archeologist 

David Bakke Regional Pesticide Use Coordinator 

Lynda Karns Forest NEPA Coordinator 

Connie Hendryx Document Preparation 

Others consulted during the analysis process: 

William Stephans Agriculture Commissioner, Siskiyou County Dept. of Agriculture 

(SCDA) 

Patrick Griffen Deputy Agriculture Commissioner, (SCDA) 

Smokey Thornhill Deputy Agriculture Commissioner, (SCDA) 

Butch Krebs Biologist, California Department of Food and Agriculture 

Patrick Akkers California Department of Food and Agriculture 

Bob Farnum Weed Specialist, Amador County Department of Agriculture 

Suzanne Ebright Weed Specialist Plumas/Sierra Counties Dept. of Agriculture 

Laura Finley Biologist, U.S. Fish and Wildlife Service 

Garwin Yip Biologist, National Marine Fisheries Service 
SALMON RIVER Knapweed Environmental Assessment 67

Fred Blatt Environmental Specialist, North Coast Regional Water Quality Control 

Board 

William Winchester Biologist, North Coast Regional Water Quality Control Board 

Frank Reichmuth, North Coast Regional Water Quality Control Board 

Stephen Wratten Chemist, Monsanto Corp. 

Kathy Brunetti California Department of Pesticide Regulation 

Jerry Cambell California Department of Pesticide Regulation 

Lily Tomlin North Coast Laboratories 

Celestine Duncan Weed Management Services Consultant 

Steve Orloff Farm Advisor, U.C. Davis Agricultural Extension 

Joe DiTomaso Research Scientist, U.C. Davis 

Vivian Parker Resource Protection Associate, Indian Basket Weavers Association 

Patty Clary Executive Director, Californians for Alternatives Against Toxics 

Alvis Johnson Karuk Tribe 

Harold Tripp Karuk Tribe 

Paula McCarthy Karuk Tribe 

Laverne Glaze Indian Basket Weavers Association 

Verna Reese Indian Basket Weavers Association 

Rene Stauffer Indian Basket Weavers Association 

Roy Lincoln Chairman, Quartz Valley Reservation 

Jesse Rose Allen Salmon River Native Americans 

Jim Bennett Salmon River Native Americans