Tech Note
Snake Repellents
April 2003
Wildlife Services
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 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.
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://www.epa.gov/opprd001/inerts/lists.html.
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 oil: 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 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
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/nwrc.
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 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, DC 20250–9410 or call (202) 720–5964
(voice and TDD). USDA is an equal opportunity provider and employer.
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