Wildlife Services Tech Note

Snake Repellents

Wildlife Services (WS), a program within the U.S. Department of 

Agriculture’s (USDA) Animal and Plant Health Inspection Service 

(APHIS), provides Federal leadership to help manage invasive 

brown treesnake (Boiga irregularis) populations on Guam and 

the Northern Marianas Islands. WS and its partners aim to reduce 

snake damage on the islands and minimize the accidental export 

of this invasive species to Hawaii or the continental United 

States. Brown treesnakes were accidentally introduced to Guam 

in the late 1940s or early 1950s hidden away in cargo shipments.

WS employees use a variety of management methods, such as 

trapping, acetaminophen toxicant baits, and the use of snakesniffing detector dogs, to reduce snake numbers, particularly 

around military bases, airports, and shipping ports. Research 

also shows that cinnamon oil, clove oil, and eugenol are effective 

snake repellents. Snakes will retreat when sprayed directly with 

these oils and will exit cargo or other confined spaces when 

these oils are introduced to the area.

Certain substances used to mitigate pests are exempt from the

requirement for federal registration under the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA), as amended. 

Products containing cinnamon oil (CAS No. 8015-91-6), clove 

oil (CAS No. 8000-34-8), and eugenol (CAS No. 97-53-0) are 

exempt from FIFRA registration requirements when used as 

pesticide active ingredients at non-food use sites to repel brown 

treesnakes, provided they meet the conditions established by 

both the U.S. Environmental Protection Agency (www.epa.gov/

minimum-risk-pesticides/conditions-minimum-risk-pesticides) 

and the Guam Environmental Protection Agency. These 

conditions include:

 Cinnamon oil, clove oil, and eugenol are used alone or in 

combination with other active ingredients exempted under 

FIFRA Section 25(b) and listed under 40 CFR 152.25(f)(1). The 

list of acceptable active ingredients may also be obtained at: 

www.epa.gov/minimum-risk-pesticides/active-ingredientsallowed-minimum-risk-pesticide-products.

 They can be mixed only with FIFRA Section 25(b) inert 

ingredients listed under 40 CFR 152.25(f)(2), commonly 

consumed food items in 40 CFR 180.950(a), animal feed items 

Brown treesnakes are an invasive species on Guam. Photo by WS

in 40 CFR 180.950(b), edible fats and oils in 40 CFR 180.950(c),

 and/or substances listed under 40 CFR 180.950(e). The list of 

acceptable inert ingredients may also be obtained at: www.

epa.gov/minimum-risk-pesticides/inert-ingredients-approveduse-minimum-risk-pesticide-products.

	 All product containers are labeled, according to Guam’s 

pesticide law and implementing regulations (www.

guamcourts.org/compileroflaws/GAR/22GAR/22GAR003-15.

pdf). The label must include the name and percentage by 

weight of each active ingredient, all the names of each inert 

ingredient, and the name and contact information of the 

producer (WS State Program contact).

This tech note describes how to use cinnamon oil, clove oil, and 

eugenol to repel brown treesnakes, per the requirements of 

FIFRA Section 25(b).

Endangered Species Considerations

Before using any of these substances as a snake repellent, consult 

with appropriate wildlife authorities to ensure its use is not 

hazardous to any threatened or endangered species. It may be 

necessary to obtain a permit from the U.S. Department of the 

Interior’s Fish and Wildlife Service and/or the applicable State or

local wildlife agency before repellents may be used. The applicator 

is responsible for obtaining all required permits and licenses.

www.aphis.usda.gov/wildlife-damage

USDA is an equal opportunity provider, employer, and lender.

APHIS 24-002 | Revised November 2023
Once a brown treesnake is detected in cargo, repellents may be 

used to flush it out. Photo by WS 

Repellent Oils

Any commercially available cinnamon oil, clove oil or eugenol 

with 95 percent or greater purity are acceptable for use in brown 

treesnake repellent mixtures. 

Aerosol Spray Mixture and Application

Cinnamon oil, clove oil, and eugenol aerosol sprays are effective 

for repelling snakes. Repellent spray mixtures should contain:

 One percent active ingredient (either cinnamon oil, clove oil, 

or eugenol)

 One percent sodium lauryl sulfate (CAS No. 151-21-3; a FIFRA 

Section 25(b) active ingredient)

 Ninety-eight percent water (a FIFRA Section 25(b) 

inert ingredient)

Spray the mixture directly on the snake, aiming for its head. 

Direct contact with the snake will trigger escape behavior. To be 

effective, the spray must come in direct contact with the snake. 

Applying the mixture to hard surfaces will not prevent snakes 

from entering areas.

Vapor Fumigant Application

Cinnamon oil, clove oil, and eugenol may also be used to 

fumigate enclosed spaces. To prepare, saturate a piece of 

absorbent material with one of the oils. Use only unadulterated 

oils. Pass hot air directly over the saturated absorptive material 

to volatilize the oils. DO NOT USE OPEN FLAMES TO HEAT THE 

OILS. The heated air should be no hotter than 200 degrees 

Fahrenheit, or no hotter than 10 degrees Fahrenheit below the 

flash point of the oil being used. The flash point for eugenol is 

230 degrees Fahrenheit, and the flash points for cinnamon oil 

and Clove oil are 200 degrees Fahrenheit.

Direct the heated air into containers, cargo spaces, house 

crawl spaces, or other enclosed spaces where snakes may be 

located. Snakes will emerge and vacate the treated space. This 

application method is only effective for driving snakes out 

of enclosed spaces. These oils will not prevent snakes from 

entering enclosed spaces.

Storage and Disposal

Store oils in the original container. Recycle containers or dispose 

of them in an appropriate landfill.

Potential Hazards

Potential hazards to applicators are low unless the person is 

allergic to the oil being used. If eye irritation occurs, flush with 

water for 15 minutes. If the applicator has trouble breathing, 

move to fresh air and call a physician. Clove oil and eugenol are 

known fish anesthetics, and therefore should not be applied 

directly to water.

More Information

Call WS’ National Wildlife Research Center at (970) 266-6000 or 

visit www.aphis.usda.gov/wildlifedamage/nwrc to learn more 

about these repellents.

You can find information on using this method for removing 

brown treesnakes from cargo in the following article: 

Clark, L., C. Clark, and S. Siers. 2017. Brown Tree Snakes: Methods 

and Approaches for Control. Pages 107-134 in Pitt, W. C., J. Beasley, 

and G. W. Witmer, editors. Ecology and Management of Terrestrial 

Vertebrate Invasive Species in the United States. CRC Press, Boca 

Raton, Florida, USA. (nwrc.contentdm.oclc.org/digital/collection/

NWRCPubs1/id/60458/rec/6)

For information about the availability of these products, contact 

your WS State Director at 1-866-4USDAWS (1-866-487-3297) or 

WS’ Pocatello Supply Depot at (208) 236-6920. In Guam, call (671) 

635-4400.