Exhibit 5c CT_CNG_Adjuvants.pdf

Appendix J of the August 2021 Record of Decision for Caribou-Targhee National Forest and Curlew National Grassland Integrated Weed Management Analysis

Exhibit 3.

ADJUVANTS

Adjuvants are specially designed chemicals that are added to an herbicide solution to modify the performance of the total spray mixture. Adjuvants are not regulated by the EPA in the same way that pesticides are. The EPA does not register or approve the labeling of spray adjuvants. Field testing is generally completed by the adjuvant manufacturer (Bakke 2007). Labels accompanying adjuvants describe their properties and prescribe use rates. Information on types of adjuvants to use can also be found on herbicide labels and in publications by university extension services (Prather et al. 2011, Zollinger 2012).

Adjuvants perform various functions, including: enhanced plant uptake of the herbicide; better mixing of otherwise incompatible herbicides; increased adhesion of the spray to plant surfaces;

and reduced spray drift. In many herbicide products, adjuvants are included as part of the pre-mixed formulation as purchased. Applicators can also add adjuvants to spray mixtures prior to application.

For many pesticide products containing adjuvants as part of the formulation, the compounds are not explicitly identified on the label or the Safety Data Sheets (SDS). Unless they are on one of US EPA’s lists of more toxic chemicals, they do not have to be identified. The identity of these ingredients in a pesticide or adjuvant product is legally protected from full disclosure as “Confidential Business Information.”

At least one adjuvant is known to pose hazards to aquatic wildlife—the surfactant used in the original formulation of RoundUp®, polyoxyethyleneamine (POEA). This surfactant is more toxic to aquatic life than the active ingredient glyphosate. The POEA adjuvant (Roundup Pro) will only be used in uplands where there is no potential for movement into aquatic systems.

Within or near aquatic systems, only products labelled for aquatic application would be used.

Adjuvants used on the Caribou-Targhee National Forest is identified below in Table J-1.

Adjuvants with low toxicity to wildlife include modified seed oils, alkyl ethoxylates, and silicones. The most commonly used adjuvant is marker dye and it is analyzed in “Use and Assessment of Marker Dyes Used with Herbicides” (Pepling, Howard, Durkin, 1997).

“Activator” adjuvants enhance activity of an herbicide’s active ingredient, while “special purpose or utility modifier” adjuvants offset common problems occurring during application, including poor water quality or foam produced during agitation of the spray mixture (Bakke 2007). Many adjuvants have properties that place them on a continuum between these two definitions and function both as activators and utility modifiers. Special purpose or utility adjuvants are used to offset or correct certain conditions associated with mixing and application such as impurities in the spray solution, extreme pH levels, and drift. These adjuvants include acidifiers, buffering agents, water conditioners, anti-foaming agents, compatibility agents, and drift control agents. Acidifiers enhance absorption of weak acid type herbicides. Drift reduction agents will generally increase the average droplet size. Defoamers reduce foaming that occurs during agitation of the spray mixture. Colorants or dyes help applicators determine what area was treated. This helps to prevent skips and overlaps and treatment of non-target areas. They reduce the chance of human exposure to recently treated vegetation (Bakke 2007).

Table J-1. Recommended adjuvant type by herbicide.

HERBICIDE RECOMMENDED ADJUVANT TYPES

2,4-D Non-ionic surfactants (NIS), fertilizer, crop oil concentrate

Aminopyralid NIS

Chlorsulfuron NIS, seed oil, organosilicone

Clopyralid NIS, crop oil concentrate

Dicamba Any as allowed by label

Glyphosate NIS

Imazamox NIS, seed oil, organosilicone

Imazapic NIS, seed oil, organosilicone

Imazapyr NIS, seed oil

Imazamox NIS, fertilizer, seed oil, petroleum/crop oil concentrate

Metsulfuron methyl NIS, seed oil, organosilicone

Picloram None needed but can add as per surfactant manufacturer’s label

Sulfometuron methyl Any allowed by label

Triclopyr triethylamine salt (TEA) NIS

Note: Recommended by Prather et al. 2011, and product labels.

Surfactants (surface active agents) are a broad category of activator adjuvants designed to improve or facilitate the dispersing/emulsifying, absorbing, spreading, sticking and/or pest-penetrating properties of the spray mixture. Pure water will stand as a droplet, with a small area of contact with the waxy leaf surface. Water droplets containing a surfactant will spread in a thin layer over a waxy leaf surface (Bakke 2007).

Post-emergence herbicide effectiveness depends on spray droplet retention and herbicide absorption by weed foliage. Adjuvants and spray water quality influence post-emergent herbicide efficacy (USDA Custer National Forest 2006). Because post-emergence herbicide effectiveness is greatly influenced by plant factors such as age, size and the growing conditions encountered before application, herbicide performance can vary. A way to minimize the variations in post-emergence herbicide performance is to use an adjuvant or surfactant in the spray solution.

Surfactants generally improve the effectiveness of post-emergence herbicides. Typically, surfactants are not added to herbicides that are soil applied (pre-emergence) (Zollinger 2012).

Surfactants used on both Forests include non-ionic surfactants, methylated or ethylated vegetable oils, nitrogen sources, and organosilicone/silicone surfactants.

Non-ionic surfactants (NIS) are all-purpose surfactants comprised of linear or nonyl-phenol alcohols and/or fatty acids. This class of surfactant reduces surface tension of water and improves spreading, sticking and herbicide uptake (USDA Custer NF 2006). Often, non-ionic surfactants will have additional additive properties, as described on their label.

Methylated or Ethylated vegetable (seed) oils (MSO) are produced by reacting fatty acids from seed oils (corn, soybean, sunflower, and canola) with an alcohol to form esters. The methyl or ethyl esters produced by this reaction are combined with surfactants/emulsifiers to form esterified seed oil. These surfactants reduce surface tension of water and improve herbicide uptake by improving herbicide distribution on the leaf surface (USDA Custer NF 2006). Adverse environmental conditions such as low humidity, hot weather, lack of rain, drought-stressed weeds, or weeds not actively growing due to some environmental stress favor the use of MSO.

These oils are more effective than non-ionic surfactants as an adjuvant to post-emergence herbicides (Zollinger 2012).

Nitrogen sources typically consist of premixed combinations of various forms of nitrogen and surfactants. They generally are used with herbicides recommending the addition of ammonium sulfate or 28 percent nitrogen. These surfactants reduce surface tension of water and improve leaf surface spreading (Miller and Westra 1998). They are used primarily with broadleaf herbicides.

Fertilizers containing ammonium nitrogen have increased the effectiveness of herbicides like glyphosate, and 2, 4-D amine. Fertilizer applied with other herbicides may reduce weed control or cause crop injury. Some fertilizers enhance non-target plant growth to stimulate competition from weed species re-establishing. Fertilizers should be used with herbicides only as indicated on the label or where experience has proven acceptability (USDA Custer NF 2006).

Organosilicones and silicone surfactants are two types of nonionic surfactants. Organosilicone surfactants drastically reduce surface tension of water to the point where the herbicide droplets thin and coalesce to form a thin layer on the leaf surface (known as “superspreading”). In addition, this class of surfactant provides improved effectiveness through maximum rainfastness (Tu et al. 2001).

See Table J-2 for details about adjuvants, categories, product names, and other information.

Table J-2. Adjuvant type, class, product, and product manufacturer.

ADJUVANT

TYPE CATEGORY PRODUCT

NAME

PRODUCT

MFG.

PRINCIPAL

FUNCTIONING AGENTS

USE

RANGE

SIGNAL

WORD COMMENTS

Activator

Non-ionic surfactant

(NIS)

Activator 90

Loveland

Alkylphenol ethoxylate, alcohol ethoxylate and tall oil fatty acid

0.125–0.5%

Caution

Low foam, biodegradable, non- flammable

R-11

Wilbur-Ellis

Alkylphenol ethoxylate, butyl alcohol, dimethylpolysiloxane

0.063–1%

Warning Spreader, activator

Spreader 90

Alkylpolyethoxy ethers and ethoxylated derivatives

8–64 oz/ 100 gal

Warning

Spreader

Super Spread 90

Alkyl aryl polyoxyethylene glycols and free fatty acids

0.25–0.5%

Spreader

ADJUVANT

TYPE CATEGORY PRODUCT

NAME

PRODUCT

MFG.

PRINCIPAL

FUNCTIONING AGENTS

USE

RANGE

SIGNAL

WORD COMMENTS

Basic Blend and

Methylated or Ethylated

Vegetable Oil and

Nonionic Surfactant and

Nitrogen Source

Renegade

Modified vegetable oil, ammonium solution, nonionic surfactant

1–2.5%

Warning

Unique blend, high load of

Nitrogen

Methylated or Ethylated

Vegetable Oil

MSO with Leci- Tech

Loveland Methylated seed oils plus emulsifying surfactants

1–2 pt/A

MSO and non-ionic

Activator - Syl-tac Wilbur-Ellis Organosilicone/ modified vegetable seed oil

0.125–

0.375% Caution -

Methylated or Ethylated

Vegetable Oil and

Organo-

Silicone Surfactant

Phase

Methylated seed oil plus organosilicone surfactant

0.125–0.5% and

Utility Modifier

Nonionic Surfactant and

Buffering

Agent or Acidifier

Super Spread

7000, LI 700

Alkyl aryl polyoxyethylene, ethoxylated alcohols, aliphatic polycarboxylate

0.25–4 pt/100 gal

Utility

Modifier

Colorant Hi-Light Becker-

Underwood Proprietary blue colorant 6–32 oz/100 gal Caution -

Bullseye Milliken Chemical Proprietary blue colorant 0.5 oz/gal None -

Water Conditioning

Agent and Buffering Agent or Acidifier

Bronc Max

AMS/ammonium alkyl aryl sulfonates, polycarboxylic acid

0.125–1%

Ammonium sulfate (AMS) replacement

Water

Conditioning Agent

Choice Weather Master

Blend of salts of polyacrylic, hydroxy carboxylic, propionic acids, phosphate ester, ammonium sulfate

0.25–0.5%

AMS, water conditioner