APHIS ech Note

Wildlife Services

June 2003

Snake Repellents

Wildlife Services (WS), a program within the U.S.
Department of Agriculture's (USDA) Animal and Plant
Health Inspection Service (APHIS), uses several
methods to manage brown tree snake populations on
Guam and the Northern Marianas Islands. The
purpose of these management efforts is to reduce
the number of brown tree snakes, particularly around
military bases, airports, and shipping ports, in order
to minimize the risk of accidently exporting this
invasive species to Hawaii or the continental United
States. Brown tree snakes were first introduced to
Guam in the late 1940s or early 1950s hidden away
in cargo shipments.

Effective Snake Repellents

Snake management methods used by WS
include trapping and the use of snake-sniffing
detector dogs. To improve these management
methods, research is underway to develop toxicants,
reproductive sterilants, improved trap lures, and
chemical repellents.

Research has shown that cinnamon oil, clove ail,
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.

On March 6, 1996, the U.S. Environmental
Protection Agency (EPA) published in the Federal
Register a notice exempting certain minimum risk
pesticides from regulation under the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA).
The exemption, issued by EPA under the authority of
FIFRA Section 25(b) and codified at 40 Code of
Federal Regulations (CFR) 152.25, applies to
cinnamon oil, clove oil, and eugenol. These materials
are exempt from the requirements of FIFRA when
used as pesticide active ingredients provided that:

1. They are used alone or in combination with other

active ingredients exempted under FIFRA 25(b);
2. They contain only EPA List 4(A) inert ingredients.

The list of acceptable inert ingredients may be

obtained from the following Web site:

http:/Awww.epa.gov/opprd00 1/inerts/lists.htm|.

While cinnamon oil, clove oil, and eugenol are
exempted from Federal regulation under FIFRA
Section 25(b), they are not automatically exempt from
regulation by the State or Territory in which they are
used. Before using any of these materials as a
snake repellent, contact the territory or State agency
responsible for pesticide regulation to determine
whether additional regulatory requirements apply.

Endangered Species Considerations

Before using any of these materials as a snake
repellent, consult with appropriate wildlife authorities
to ensure that the use does not present a hazard 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. Obtaining all required
permits and licenses is the responsibility of the
applicator.

General Information

Any use of cinnamon oil, clove oil, and eugenol
to manage snakes must comply with information in
this tech note. A copy of this tech note must be in
the possession of any individual applying these oils
to manage snakes.

Obtaining Repellent Oils

Applicators may obtain oils from any retail or
wholesale chemical supplier. Any commercially
available brand with 95 percent or greater food-grade
oil is acceptable. When ordering these products, use
the information below:
+ Cinnamon oil: CAS No. 8015-91-6
+ Clove ail: CAS No. 8000-34-8
+ Eugenol: CAS No. 97-53-0.

Aerosol Spray Application

Cinnamon oil, clove oil, and eugenol aerosol
sprays are effective for moving snakes. Spray
mixtures should be formulated to contain:

+ One percent active ingredient (either cinnamon,
clove, or eugenol oil)

+ One percent sodium lauryl sulfate

+  Ninety-eight percent water.

To use, 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.
Application 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
ails. 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 applica-
tion 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

Applicator hazards are not expected, unless the
applicator is allergic to the oil being used. If eye
irritation occurs, flush with water for 15 minutes. If
breathing difficulty occurs, remove person to fresh air
and call a physician. Clove oil and eugenol are known
fish anesthetics, and therefore should not be applied
directly to water.

Additional Information

Additional information on these repellents may be
obtained by calling WS’ National Wildlife Research
Center (NWRC) at (970) 266-6000 or by visiting
NWRC's Web site at:
http://www.aphis.usda.gov/ws/nwre.

Additional information is also available in the
following publication: Clark, L. and J. Shivik. 2002.
Aerosolized essential oils and individual natural
product compounds in brown tree snake repellants.
Pest Management Science 58:775-783.

For further 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.

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 orienta-
tion, 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, 14th and
Independence Avenue, SW, Washington, DC 20250-9410 or call
(202) 720-5964 (voice and TDD). USDA is an equal opportunity
provider and employer.

United States Department of Agriculture * Animal and Plant Health Inspection Service

Safeguarding American Agriculture