Senior
Seminar 2002
Introduced Species in Hawaii
Termites
Coptotermes
formosanus
Common
Name: Formosan subterranean termite
C.
formosanus soldier
Photo courtesy of: Agricultural
Reasearch Service
Introduction
Of the eight species of introduced termites, Coptotermes
formosanus has created the greatest economic damage and
is the cause of greatest concern for the Hawaiian Islands (Grace et al.
2002). C. formosanus and the other termites came to the islands
on boats following World War II. The
University of Hawaii continues to be a center of research into the biology,
behavior, and control of this pest. The future looks promising as old
methods of management are refined, and new methods are developed.
C.
formosanus queen
Photo courtesy of:
Agricultural Research Service
Description
Coptotermes formosanus is
a generalist, colonial, social insect building colonies either above or
below ground (Howarth 1985). Termites have a caste system including: a
king, queen, workers, soldiers, and reproductives or alates (winged termites).
The workers provide the food, soldiers defend the nest, and reproductives
breed the colony. The colony is led by a queen who has a life span of
approximately 15 years and is capable of producing up to 2,000 eggs a
day. The workers and soldiers may live 3-5 years with caste proportions
of approximately 360 workers: 40 soldiers (Grace et al. 1996a). A colony
is surrounded by an extensive foraging system consisting of tunnels underneath
the ground, with a mature colony containing millions of termites (Tulane
2002, ARS 2002). Grace et al. (1995) found older and less vigorous
colonies contained workers who had a larger body mass than workers in
younger colonies. The diet of the subterranean termite consists of anything
that contains wood fiber (homes, building, live trees), crops, and plants.
Live trees include: Oak, Ash, and water-bound Cypress (ARS 2002). Crops
include sugarcane (Broughton and Grace 1994).
C.
formosanus cartonous nest
Photo courtesy of: Agricultural
Research Service
In addition
to C. formosanus, there are seven other species of introduced
termites to the Hawaiian Archipelago:
Coptotermes vastator
Common Name: Philippine milk termite
Limited distribution in Hawaii. Most serious pest in Guam and the Philippines.
Interactions with C. formosanus may limit its distribution in
Hawaii (Grace et al. 2002).
Cyptotermes
cynocephalus
Common Name: Indo-Malaysian termite
Collected on Oahu, although only in a very limited area. Found among dead
vegetation rather than structural timbers (Grace et al. 2002).
Cryptotermes
brevis
Common Name: West Indian drywood termite
Long-term resident of Hawaii. Commonly found in buildings (Grace et al.
2002).
Incisitermes
immigrans
Common Name: Lowland tree termite
Long-term resident of Hawaii. Occasionally infests structural lumber (Grace
et al. 2002).
Neotermes
connexus
Common Name: Forest tree termite
Long-term resident of Hawaii (Grace et al. 2002).
Incisitermes
minor
Common Name: Western drywood termite
Most important dry wood termite pest in California. Found infesting two
buildings in different parts of Oahu (Grace et al. 2002).
Zootermopsis
angusticollis
Common Name: Pacific dampwood termite
Well established at high elevation on Maui. Found in California and Oregon.
Usually occurs in logs and other dead wood matter on the ground. Only
attacks structural wood when the wood is wet or decayed (Grace et al.
2002).
Distribution
C.
formosanus is native to China and the South Pacific.
In the U.S., C. formosanus has been found in
Alabama, California, Florida, Georgia, Hawaii, Louisiana, Mississippi,
North Carolina, South Carolina, Tennessee, and Texas (ARS 2002). It is
found on all the major islands of Hawaii (Grace et al. 2002).
United States Distribution Map for C. formosanus
Photo courtesy of: Agricultural
Research Service
Vectors
After World War II, military ships returning to Hawaii
and the continental states from the Pacific transported the termite to
the islands (Tulane 2002). Wooden boats, shipping containers, and wooden
products were ideal habitats for the termite on its way Hawaii (Broughton
and Grace 1994).
Broughton and Grace (1994) found low genetic variation in the C. formosanus
populations of the Hawaiian Islands. They believe the current populations
have all come from the same Chinese source population. A bottleneck effect
may have occurred where the introduction of C. formosanus represents
only a single genetic lineage, such as an invasion by a single colony.
Why
C. formosanus is successful
C. formosanus is able to tunnel
below soil treated with chemicals, bypassing human efforts to control
termites. They are also able to tunnel through asphalt, plaster, and synthetic
materials such as plastic. They have fairly minimal needs, a small amount
of water and food can support a large colony (Tulane 2002).
C. formosanus thrives on Douglas-fir wood, a lumber product which
is widely used in Hawaii and is resistant to chemical preservatives (Grace
and Yamamoto 1994).
Impacts
C. formosanus is the most economically
serious pest in Hawaii, costing residents $100 million a year (Tulane
2002). Historic structures in Hawaii have been threatened, such as Iolani
Palace in Honolulu (Grace et al. 2002).
Damage to the southern United States by C. formosanus has cost
$1 billion a year. In New Orleans, 30-50% of the city's 4,000 historic
live Oak trees are believed to be infected with total damage costing the
city $300 million a year (Tulane 2002).
Impacts of increased use of pesticides to control the termite population
has lead to higher costs for homeowners and destructive effects on the
environment, including contamination of water supplies caused by runoff
(Yates et al. 2000).
Live trees are attacked as well as century old structural timbers
Photo courtesy of: Agricultural
Research Service
Management
The majority of efforts to control termites in the Hawaiian
Islands are aimed at C. formosanus. Various methods are used
to prevent and control this termite: physical barriers, preservative treated
wood, naturally resistant woods, soil insecticide applications, and baiting
systems (Grace et al. 2002).
Physical Barriers:
Particle barriers are a common form of physical barrier to termite penetration
and can be made of a variety of substances: crushed basalt, silica sand,
natural sand, granite, glass shards, limestone, quartz and coral sand,
concrete, or brick (Yates et al. 2000).
The Basaltic Termite Barrier (BTB) was invented in Hawaii and is a non-chemical,
physical barrier used to prevent termite tunneling. This screened particle
barrier consists of crushed basaltic rock, screened to particle size such
that termites are unable to penetrate. The termites are unable to move
the particles with their mandibles, the tiny rocks are too hard for the
them to crush, and it packs together too tightly for the termites to find
a way through. BTB is used in all State Government construction in Hawaii
and by architects in residential construction (Grace et al. 2002).
TermiMesh was invented in Australia and is a stainless
steel screen commonly used in new construction to prevent termite penetration
(Grace et al. 2002). Grace et al. (1996c) found TermiMesh to be an excellent
preventative measure so long as it is properly installed ensuring there
are no cracks between the product and unit of attachment. Cracks would
enable the termites to invade and destroy the structure.
Preservative-treated wood:
Preservatives applied to wood may prevent termite attacks. Hawaii is unique
among the United States in that it is the only state requiring all structural
lumber used in new building construction to be pressure treated with a
wood preservative. Chromated copper arsenate (CCA) and disodium octaborate
tetrahydrate (DOT) are the most widely used preservatives for wood in
Hawaii (Grace et al. 2002). Borate is of lower environmental impact when
compared to other preservatives. An additional benefit of borate is it's
fire-resistant properties. However, borate does not work well with solid
wood, it only can be used with oriented strandboard. Sean et al. (1999)
found 1% zinc borate to provide good protection against termite attack.
Insecticide:
This is applied to the soil to prevent a termite attack.
Chlordane, once a popular insecticide, has not been used since 1986 in
Hawaii due to human health and safety dangers (Tulane 2002). As a consequence,
less toxic chemicals have been used as replacements such as: imidacloprid
and fipronil (Grace et al. 2002). These newere chemicals have reduced
longevity and consequently are applied more heavily than their more toxic
counterparts (Tamashiro et al. 1990, in Yates et al. 2000). 20 years of
field research at the University of Hawaii has shown pyrethroid insecticide
permethrin to be long-lasting under tropical conditions. Grace et al.
(1995) found termites to differ widely, under laboratory conditions, in
their susceptibility to insecticides.
Naturally resistant woods:
Hawaii has recently seen a decrease in the use of plantations for growing
food crops such as sugar and pineapple. Consequently there is an interest
in using the land for forestry. There would be many benefits to growing
termite resistant tree species that could be used as lumber for construction.
Grace et al. (1996a) studied termite resistance among different species
of Hawaiian-grown trees. The species with the greatest potential for termite
resistance were: Cryptomeria japonica (Sugi, Taxodiaceae), Eucalyptus
microcorys (Tallowwood, Myrtaceae), and Thespesia populnea
(Milo, Malvaceae). The benefits of using naturally resistant woods are
they are more environmentally-friendly and less toxic, than preservative
treated wood. Locally grown trees would relieve the need for importation
of both wood and chemicals. In addition, naturally durable wood has a
higher market value than less durable wood (Grace et al. 1996a).
Baits:
In-ground and above-ground bait stations are used as a post-introduction
termite control method and are ineffective when used as a preventative
measure (Yates and Grace 2000). Hexaflumuron, a toxin to termites, was
first used commercially in Hawaii and Florida for C. formosanus
control. Baits have proven effective in Hawaii and are used to protect
historic structures. They are an appealing method of termite control because
this cryptic social species is able to be eliminated by a single application
of a small amount of insecticide. Those termites who come in contact with
the insecticide transmit it to other members of the population (Grace
et al. 1996b).
Placement of a monitoring/baiting station
Termite bait trap in New Orleans sidewalk
Courtesy of: Agricultural
Research Service
What
to do if you have termite problems:
Eliminate water sources at home by: not
allowing wood to have contact with wet soil, replacing wood structures
that are water-damaged, fixing leaky plumbing, fixing cracks in walls,
concrete, and roof.
If you live in an area that is prone is infestation, you should have your
home frequently monitored for signs of infestation by a qualified pest
control operator (Tulane 2002).
The
Future
The University of Hawaii continues research efforts, examining the molecular
genetics of C. formosanus colonies. This will enable us to better
understand how termites spread and distribute themselves, how different
colonies interact, and the dynamics of social organization within a colony.
This research will also help scientists in distinguishing between the
various species of termites so as to better determine the efficacy of
bait stations. Also of interest is greater understanding and manipulation
of termite biology and behavior in order to develop more effective and
environmentally sound termite control methods.
Links
The Quest
for Environmentally Friendly Termite Control
The University of Georgia College of Agricultural and Environmental Sciences.
Excellent web
site devoted to environmentally safe methods for termite control. Has
lots of links to other sites containing general information, pest control
information, and research by universities.
http://www.uga.edu/caes/insectlab/termlinks.html
National Formosan Subterranean
Termite Program
US Department
of Agriculture's Agricultural Research Service (ARS)
They are joining together with other governmental agencies, private organizations
and universities to develop tools and strategies for dealing with termites.
Their goal is to suppress termites with minimum cost and pesticide use.
Plans include evaluating existing technologies and developing new ones.
http://www.ars.usda.gov/is/fullstop/
University of Hawaii Termite
Project
Highlights of the site include: current research topics, lots of links,
and a free newsletter entitled the Termite Times.
http://www2.hawaii.edu/~entomol/
Bibliography
Agricultural
Research Service (ARS). April 2002. Agricultural Research Service Formosan
Subterranean Termite Frequently Asked Questions. URL http://www.ars.usda.gov/is/fullstop/faqhome.htm
(10 Oct 2002).
Agricultural Research Service (ARS). April 2002. Agricultural Research
Service Formosan Subterranean Termite Program Information. URL http://www.ars.usda.gov/is/fullstop/backgrounder.htm
(10 Oct 2002).
Broughton,
R. E., and J. K. Grace. 1994. Lack of mitochondria-DNA in an introduced
population of the formosan subterranean termite (Isoptera: Rhinotermitidae).
Sociobiology 24: 121-126.
Grace, J. K., D. M. Ewart, and C. H. M. Tome. 1996a. Termite resistance of wood species grown in Hawaii. Forest Products Journal 46: 57-60.
Grace, J. K., R. J. Woodrow, and J. R. Yates. 2002. Distribution and management of termites in Hawaii. Sociobiology 40: 87-93.
Grace, J. K., C. H. M. Tome, T. G. Shelton et al. 1996b. Baiting studies and considerations with Coptotermes formosanus (Isoptera: Rhinotermitidae) in Hawaii. Sociobiology 28: 511-520.
Grace, J. K., and R. T. Yamamoto. 1994. Simulation of remedial berate treatments intended to reduce attack on douglas-fir lumber by the formosan subterranean termite (Isoptera: Rhinotermitidae). Journal of Economical Entomology 87: 1547-1554.
Grace, J. K., R. T. Yamamoto, and M. Tamashiro. 1995. Relationship of individual worker mass and population decline in a formosan subterranean termite colony (Isoptera, Rhinotermitidae). Environmental Entomology 24: 1258-1262.
Grace, J. K., J. R. Yates, C. H. M. Tome, et al. 1996c. Termite-resistant construction: use of stainless steel mesh to exclude Coptotermes formosanus (Isoptera: Rhinotermitidae). Sociobiology 28: 365-372.
Howarth, F. G. 1985. Impacts of Alien Land Arthropods and Mollusks on Native Plants and Animals in Hawai'i. Pp. 149-179. In, Stone, C. P. and J. M. Scott. Hawaii's Terrestrial Ecosystems Preservation and Management.
Sean, T., G. Brunette, and F. Cote. 1999. Protection of oriented strandboard with borate. Forest Products Journal 49: 47-51.
Tamashiro, M., J.
R. Yates, R. T. Yamamoto, and R. H. Ebesu. 1990. The integrated management
of the formosan subterranean termite in Hawaii. Pp. 77-84 in:
Pest control into the 90s: problems and challenges. Applied Science Dept.,
City Polytechnic of Hong Kong.
Tulane University. Formosan Subterranean Termite. URL http://www.tulane.edu/~mrbc/2001/MRB%20Project/termite.htm
(10 Oct 2002).
Yates, J. R., and
J. K. Grace. 2000. Effective use of above-ground hexaflumuron bait stations
for formosan subterranean termite control (Isoptera: Rhinotermitidae).
Sociobiology 35: 333-356.
Yates, J.R.,
J. K. Grace, and J. N. Reinhardt. 2000. Installation guidelines for the
basaltic termite barrier: a particle barrier to formosan subterranean
termites (Isoptera: Rhinotermitidae). Sociobiology 35: 1-16.
Designed by:
Shannon Marie Murphy Contact:
murphsh@earlham.edu
Last revised:
5 December 2002