Herbicide Use & Safety Practices

For trees & shrubs

Herbicide is a tool the FireBREAK Campaign uses as part of its work to reduce invasive fire fuels in the Moab Valley. Used to prevent invasive trees from resprouting, using herbicide is an essential step in this work to keep wildfire risk in Moab reduced for the long-term.

Herbicide can understandably be a topic of concern. With this in mind, FireBREAK crews reduce risk to humans, animals, and the environment through mitigation strategies including using very small amounts of herbicide applied to individual plants.

When used sparingly and with care, herbicides are a powerful tool whose risks can be greatly reduced.

Why does FireBREAK use herbicide?

Effectiveness. When applied properly, herbicide is effective at greatly reducing, and often preventing, resprouts of some of Moab’s most persistent fire fuels, such as Russian olive and tamarisk. Without herbicide, these trees quickly regrow from cut stumps — often thicker than before — undoing the removal work within a few years.
Efficiency. Herbicide is fairly inexpensive and requires relatively little labor compared to other forms of resprout management. By using herbicide when appropriate, FireBREAK can maximize the impact of fuels removal during the five-year window of the Community Wildfire Defense Grant.
Expertise. Project partners who apply herbicide have received training on effective, safe application practices, as is explained below.

FireBREAK crew members apply herbicide to Russian olive stumps in April 2025.

How does FireBREAK reduce risks of herbicide use?

Carefully following labels. Herbicide labels are essential guides to reduce risk. They dictate many safety practices, from proper personal protective equipment to required weather conditions. Labels are also legal documents; it is a violation of federal law to use herbicides or pesticides in a manner inconsistent with their labels. As applicators, FireBREAK crews act in accordance with this law.

Taking extra care in sensitive environments. Herbicide is never applied directly into water. The FireBREAK Campaign usually uses formulations of herbicides that are aquatically approved by the EPA, meaning the formulas have undergone more rigorous testing for sensitive environments. While applying herbicide to plants near water, crews are extra-precise in their applications and always use aquatically approved herbicide if the stumps are within 10 feet of water

Following legal regulations. Every person applying herbicide in FireBREAK either has a Utah Pesticide Applicator License (which also covers herbicide) or is directly overseen by someone with that license. As a part of every application, records are kept about the type and amount of herbicide used.

Herbicide application

How are herbicides applied to trees & shrubs?

Herbicides are spot-applied to individual cut plants. There is no fogging or broadcast application.

Most applications (roughly 80%) use the “cut-stump” method. In this method, the herbicide formulation is mixed with blue dye. One crewmember will use a chainsaw to “low-stump” a tree, meaning they cut it flush with the ground. Within 10 minutes, another crewmember will apply herbicide to the ring of live tissue on the tree stump with a Nalgene bottle outfitted with a pipette nozzle. For small trees, herbicide is applied to the entire stump surface.

A pipette bottle used for herbicide application on trees and shrubs.

The herbicide is then drawn down into the plant’s root system, where it eventually kills the plant. Each tree receives less than an ounce of herbicide and that small volume becomes diluted as it spreads through the root system. Very little herbicide is left at the application site and is quickly broken down.

Typically, before low-stumping, FireBREAK sawyers will go through an area and “high-stump” all invasive trees to about hip height and clear out brush. Once that is complete, a sawyer and herbicide applicator will work through the area, conducting low-stumping immediately followed by herbicide applications. This method ensures the area is clear and open before herbicide application, reducing the chance of spills or cross-contamination on anything other than the intended stumps.

(1) As the first part of the fuels reduction process for trees and shrubs, those plants are “high-stumped” to about waist height. Limbs and brush are removed to ensure a clear, open area for herbicide application.

(2) In the second stage, stumps are “low-stumped” nearly flush with the ground and receive a thin ring of herbicide on their outer, living layer.

In some cases trees may resprout after treatment — usually if the tree is particularly large or if the low stumping process is not effective. In these cases the resprouts need to be cut and treated again. The process for cut-stump follow-up retreatments is quite similar. A crewmember will cut down any resprouts that may have emerged on the stump and re-apply herbicide in the same way onto the resprout stump. Cut materials will be carefully disposed of so they don’t resprout. (Only some properties — depending on their size and scope of work — will receive cut-stump retreatments from grant-funded crews. All landowners are expected to conduct their own retreatments following FireBREAK work. It is important for landowners to monitor any removal areas on their properties and either treat resprouts or call for help to do so. If there are a lot of seeds in the soil, saplings may emerge in recently cleared areas. These can be pulled if caught quickly enough. Rim to Rim has weed wrenches available to aid in this process.)

Other potential application methods include basal bark (applying herbicide to the lower bark of a small tree) or foliar spray (spot-spraying leaves of individual plants). Neither of these will be commonly used but are necessary to treat some additional invasive species such as tree of heaven.

Herbicides

Which herbicides does FireBREAK use on trees & shrubs?

The FireBREAK Campaign uses two main herbicides: glyphosate and triclopyr. Glyphosate is typically used on Russian olive and triclopyr on tamarisk, though both herbicides can be used on either plant.

See below for more details about each type of herbicide.

Active ingredient name

Glyphosate

Triclopyr

Common brand name/formulation

AquaNeat, Rodeo*

Garlon 3A, Triclopyr 3, Tahoe 3A

How it works

Glyphosate is an amino acid inhibitor that prevents plants from making certain proteins that are needed for growth. Specifically, glyphosate stops the shikimate pathway. (1)

Triclopyr is an artificial form of a plant hormone called auxin. Auxin is a growth hormone. When applied at effective doses, triclopyr causes vigorous plant growth often beyond what a plant can sustain, causing it to die. (2)

Plant it’s usually used on

Russian olive

Tamarisk

Selective or non-selective

Non-selective (it will kill most plants it’s applied to)

Selective (only kills certain kinds of plants)

*Glyphosate used to be, but is no longer, the active ingredient in the commerical herbicide brand Roundup. Today, herbicide formulations available with the brand name “Roundup” include a mix of other herbicides such as triclopyr, Fluazifop-P-butyl, and/or Diquat. It is extremely important to read lables of these formulations to understand what the herbicide will affect.

Does FireBREAK use Roundup?

No, the FireBREAK Campaign does not use Roundup, which is a brand name. FireBREAK does use the herbicide glyphosate, which used to be, but is no longer, the active ingredient in Roundup. The glyphosate brand names that FireBREAK uses most frequently are aquatically-approved glyphosate formulations including brand names AquaNeat and Rodeo.

Environmental effects

Because of the way FireBREAK applies herbicide to trees and shrubs, there is limited ability for an herbicide to spread throughout the environment after application. After an herbicide is applied to a stump, it spreads throughout the plant’s root system and tissues. Plant roots have a waxy outer layer, or epidermis (similar to human skin), which allows the root to absorb water and nutrients but limits liquid loss and protects the root against external invaders, like mold (10). This waxy coating similarly holds herbicide within roots.

There are several other aspects of glyphosate and triclopyr that limit their environmental impacts.

Glyphosate

Glyphosate binds tightly to soil particles, meaning it is immobile in soils — it doesn’t move much — and is unlikely to seep into surface or groundwater. (1). Glyphosate breaks down through soil microbes into two forms of acid, AMPA acid and glyoxylic acid, which then become carbon dioxide.

Glyphosate breaks down at different rates depending on environmental conditions like sunlight exposure, but one study estimates a half-life of 8 to 9 days, with a different review of various studies estimating between a few days and 20 days (3, 11). That means within 8-9 days, 50% of the original amount of glyphosate is left in the environment, and within 16-18 days only 25% is left.

Glyphosate is also considered low in toxicity to fish and wildlife, though other products (called inert ingredients) in formulations can increase the formulation’s toxicity (1). FireBREAK uses herbicide formulations that are aquatically approved by the EPA, meaning they’ve undergone more rigorous testing for use in sensitive environments. While these formulations can cost a little more, this is one mitigation measure taken to minimize unintended impacts to soil and wildlife.

Triclopyr

Triclopyr is more mobile in soils, meaning it can move through them easily (9). However, the spot application methods used by FireBREAK limit the herbicide’s ability to breach soil in the first place. Triclopyr also breaks down relatively quickly, with an estimated half-life of 8 to 46 days (4) or 30 to 90 days (9). Triclopyr also breaks down very quickly in water that’s exposed to light — within a few days — though FireBREAK crews take care applying herbicide around water and never directly into water (4).

Triclopyr is considered slightly toxic to mammals, practically nontoxic to birds, and nontoxic to highly toxic to fish depending on the formulation (9). The salt and acid forms of triclopyr are considered nontoxic. FireBREAK uses acid and salt forms of triclopyr. (The ester forms of triclopyr are considered moderately to highly toxic. However, the ester form rapidly degrades to the acid form in the environment and fish are not likely to contact large amounts of the pesticide. (4))

What is a half-life?

A compound’s “half-life” is the time required for half of the compound to break down in the environment. After one half-life, 50% of the compound is remaining; after two half-lives, 25%; after three half-lives, 12%; and so on until the amount dwindles to nearly nothing.

For example, for an herbicide with a half-life of a week, only 6% of the herbicide will be left after a month.

Half-lives can vary widely based on environmental factors, meaning the same herbicide might break down at different rates in different places. Plus, the amount of chemical remaining after a half-life will always depend on the amount of the chemical originally applied. (1)

Human health effects

To reduce the risks of herbicide use to humans, all FireBREAK applicators use proper personal protective equipment (PPE), including long sleeves, gloves, close-toed shoes, and eye protection, while handling herbicide. They are trained in proper application and safety protocols, and take great care to avoid spills.

Low-stumping and herbicide application are typically done after all tree clearing has been completed to minimize the potential for crew members to be exposed to herbicide or drag brush through wet herbicide. In addition, applications are made with dye so that it is clear where herbicide has been applied.

Glyphosate

Glyphosate has a very low toxicity to humans and wildlife (1). With humans, the toxicity level from a glyphosate exposure to skin or through the mouth is very low compared to many other common herbicides (5). Glyphosate is listed in the EPA’s Toxicity Class III (Low Toxicity) or Class IV (Very Low Toxicity) (8).

Glyphosate doesn’t pass easily through human skin, but can cause eye or skin irritation (1). In addition, other ingredients mixed into herbicide formulations can make a product more toxic.

According to the National Pesticide Information Center (NPIC), pets may be at risk if they touch or eat plants still wet with glyphosate. Symptoms may include drooling, vomiting, diarrhea, lost appetite, or sleepiness. FireBREAK uses blue dye in all its herbicide applications so that it is clear where herbicide has been applied. If herbicide is applied in places where people walk dogs, the area will be signed until the approved re-entry period is over.

Regarding glyphosate as a potential carcinogen: there is no complete consensus about whether glyphosate causes cancer. The Environmental Protection Agency (EPA) has found no evidence glyphosate causes cancer when used in accordance with labels. This finding aligns with those of regulatory agencies in Canada, Australia, Germany, New Zealand, and the Joint Food and Agriculture Organization/World Health Organization (FAO/WHO) Meeting on Pesticide Residues (JMPR) (5). However, a panel of scientists at the International Agency on Cancer Research has deemed glyphosate “probably carcinogenic to humans” (6).

The IARC focused their studies on the overall potential hazard of glyphosate, whereas the other agencies performed risk assessments based on typical human exposure which includes applicators using appropriate PPE and other measures being taken to minimize exposure. More information about these studies can be found on the EPA and IARC websites. Additionally, the National Library of Medicine has published a paper comparing these findings.

Triclopyr

Triclopyr has low toxicity if inhaled, eaten, or applied to skin, but can cause irritation. Overall, very little triclopyr exposed to skin is actually absorbed — less than 2% in one study with human skin (4).

The formulation Garlon 3A can cause permanent eye damage (4). Because of this potential for eye damage, the EPA classifies Garlon 3A as high toxicity. Other formulations of triclopyr vary from acute toxicity to low toxicity (4). According to the NPIC, more studies need to be done to determine if triclopyr could be linked to human cancer risk (4).

References

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Information compiled by Maria Rago, Sophia Fisher, Gavin Belfry, and Kara Dohrenwend.

Last updated November 5, 2025.