field tests of molybdenum and tungsten baits - IRG. International ...

IRG/WP 04-30345
THE INTERNATIONAL RESEARCH GROUP ON WOOD PRESERVATION
Section 3 Wood Protecting Chemicals
FIELD TESTS OF MOLYBDENUM AND TUNGSTEN BAITS
FOR TERMITE CONTROL
Yoshio Katsuda 1) , Koji Nakayama 1) and Charunee Vongkaluang 2)
1) Dainihon Jochugiku Co., Ltd., 1-11, 1-Chome Daikoku-cho,
Toyonaka, Osaka 561-0827, Japan
2) Forest Products Research Division, Royal Forest Department,
Bangkok 10900, Thailand
Paper prepared for the 35 th Annual Meeting
Ljubljana, Slovenia
6-10 June, 2004
IRG Secretariat
SE-100 44 Stockholm
Sweden

ABSTRACT
FIELD TESTS OF MOLYBDENUM AND TUNGSTEN BAITS
FOR TERMITE CONTROL
Yoshio Katsuda, Koji Nakayama and Charunee Vongkaluang
Molybdenum and tungsten compounds are slow acting to termites and show a high
termiticidal efficacy. In our previous papers, we have already reported that those are
useful as termiticidal ingredients of bait formulations.
The demand for natural rubber is still on the increase. However some kinds of termites
inhabiting rubber plantations damage rubber trees and pose a serious threat.
To cope with this problem, we prepared bait stakes by having rubber tree chips
impregnated with barium salts of molybdenum and tungsten compounds and then
solidifying the mixture with phenolic-type adhesive. In field tests conducted at a
rubber plantation in Thailand, the bait stakes were hit into the ground around each
termite mound and the level of termite activities were observed at intervals. After one
and a half years from the start of the test, it was confirmed that our bait formulations
eventually eradicated termite colonies of Macrotermes and Odontotermes.
Key words : Molybdenum, Tungsten, Bait, Rubber plantation, Termite control,
1. INTRODUCTION
Macrotermes , Odontotermes
Damages by termites pose serious problems in many countries. For example, termites
often cause important damages to buildings in Japan. As main countermeasures,
termiticides such as emulsifiable concentrate and oil formulations are sprayed on
buildings and under the floor or surroundings thereof, or anti-termitic plastic sheets
containing termiticidal ingredients are employed on the ground under the floor.
Silafluofen (1-4) is regarded as an effective termiticidal ingredient, as it is
characterized by excellent properties in all aspects of termiticidal activities, safety to
mammals, chemical stabilities and so on. On the other hand, almost termiticides of
other types such as pyrethroids, organo-phosphorus compounds and carbamates which
can be used as spraying agents are difficult to be mixed with plastic resins due to
instability in alkaline environment, being unsuitable for applications to building
materials.
In China, damages by termites that eat woods or destroy embankment become social
concern, and in particular, the damage of embankment by Odontotermes formosanus,
Odontotermes hainanensis, Globitermes, or Macrotermes is serious. These kinds of
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termites make mud tubes under the embankment, and the river water in a flooded
season sinks into the mud tubes, causing a threat of destroying the embankment. To
preserve the embankment, eradication of termite colonies is indispensable, and
conventionally bait formulations containing organic chlorine-based termiticides such
as mirex have been employed for this purpose. However the use of these chemicals is
banned because of residual toxicity and environmental pollution, making the
development of new alternatives a pressing need.
Molybdenum and tungsten compounds are slow acting to termites and show a high
termiticidal efficacy. Since around the middle of 1980s, we had been engaged in
development works of applying these inorganic compounds to bait formulations. Our
first papers (5) on their mode of action suggested that the termiticidal effectiveness of
molybdenum and tungsten compounds might be much more associated with the
physiological depression caused by the accumulation of their oxides in the body,
especially in the fat body, rather than with the influences on the symbiotic intestinal
flagellates. After that, we proceeded with formulation studies and field tests aimed at
practical use in Japan and China, and reported in our subsequent papers (6-8) that
those compounds are useful as termiticidal ingredients of bait formulations.
Rubber trees are planted mainly in Thailand, Malaysia, Indonesia and Sri Lanka, and
are important as a source of supply for natural rubber whose demand is still on the
increase. At rubber plantations of these hot and humid countries, there live many
kinds of termites including Macrotermes and Odontotermes which cause damages
especially by attacking roots of young rubber trees (until 7-8 years old). In case that
rubber trees die all at once before the harvesting season of natural rubber resin, the
damages become awfully serious for the exporting nations as well as producing
farmers. Countermeasures taken for the damages in the past are only physical ones
such as removing surface soil (about 40cm in depth). In consideration of these
circumstances, we have conducted field tests of bait formulations containing
molybdenum and tungsten compounds for termite control at rubber plantations in
Thailand since July of 1999. This report deals with the test results and their high
practicability of the bait formulations.
2. MATERIALS AND METHODS
2.1. Test materials
The bait formulation served for field tests is shown in Table 1. An aqueous solution of
sodium salts of molybdic acid and tungstic acid was impregnated uniformly in rubber
tree chips, followed by the addition of an aqueous solution of barium chloride to cause
formation and precipitation of slightly water-soluble barium salts of molybdic acid
and tungstic acid. After drying, the mixture was hardened using phenolic-type
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adhesive under low pressure and then the molding was cut to give bait stakes (15x
40x250mm).
Table 1 Bait formulation for field tests
Materials Contents
Na2MoO4・2H2O (MW:242)
Na2WO4・2H2O (MW:330)
BaCl2・2H2O (MW:244)
Rubber tree chips
Phenolic-type adhesive
13.0 % (5.2% as Mo)
5.0 (2.8% as W)
15
57~61
6~10
Total 100
2.2. Test methods
Ten and more termite mounds at Phuket Rubber Experiment Station were selected as
test sites. On April of 2002, 4-6 test bait stakes (15x40x250mm) were hit into the
ground around each mound, and stakes of rubber wood (40x40x300mm) were set on
the top of each mound and around it if necessary. Then the level of termite activities at
each mound were observed at intervals. In case that damages of test bait stakes and
wood stakes were found to be serious on the observation time of October of 2002, the
stakes were replaced for new ones and the tests were continued.
3. RESULTS AND DISCUSSION
3.1. Determination of bait formulations
Ahead of this field tests, bait formulations containing sodium salts of molybdic acid
and tungstic acid, not converted to barium salts, were tested. The result was
unsatisfactory, as water-soluble sodium salts leached out during the tests. Then we
prepared solid and hard baits by hardening with phenolic-type adhesive under high
temperature and high pressure, but the baits invited a reduction in bait feeding by
termites. For this field tests therefore, barium salt-based baits were prepared by
converting sodium salts to slightly water-soluble barium salts by ion exchange method,
being free from the danger of leaching out of active ingredients. Moreover, bait
feeding by termites was found not to deteriorate as the baits can be formed porously
under low pressure.
As base materials for baits, rubber trees were suited for termites in Thailand, although
favorable base materials in Japan and China were pine trees and eucalyptus barks or
bagasse respectively. This seems to indicate diversity in bait feeding according to
termites on the spot.
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3.2. Outline of observation results after installation of baits
Results of typical test sites are summarized as Table 2.
Test
site
Table 2 Observation results
Date of installation
Date of observation
2002, 4 2002, 10 2003, 12
I ･ Five stakes were hit
into the ground around
a termite mound.
II ･ Five stakes were hit
into the ground around
a termite mound.
･ Damage was found on
one stake.
･Activities of
Macrotermes were
observed.
･ Damage was found on
one stake.
･Severe damage was
found on wood stakes.
･Activities of
Macrotermes were
observed.
･Eradication of a nest of
Macrotermes was
confirmed.
･Three satellite nests of
Hypotermes were found
around the former
termite mound.
･Live termites were not
found after digging out
a nest of Macrotermes.
･Eradication of the nest
was confirmed.
After one and a half years from the start of the test, termite mounds having a height of
about 30 cm at the beginning became flat as shown in Pictures. Thus it was confirmed
that our bait formulations eventually eradicated termite colonies of Macrotermes and
Odontotermes which attack rubber trees.
Fig. 1 Start of the test Fig. 2 After one and a half years
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After the eradication of Macrotermes and Odontotermes colonies, activities of
Hypotermes were observed. This species is known to be beneficial, as Hypotermes
termites cause no damage to rubber trees, eat fallen leaves of rubber trees to make
organic manure, and soften the soil physically.
Our bait formulations containing molybdenum and tungsten compounds utilize as
active ingredients metal elements distributed on the earth and are not possessed with
residual toxicity as organic chlorine-based termiticides, proving promising as a new
termiticide. Especially, applications of the baits to rubber plantations suffering severe
damages do a lot for the social welfare and their early practical use is expected.
4. LITERATURE
1. Katsuda, Y., H. Hirobe & Y. Minamite (Assignee: Dainihon Jochugiku)(1986).
Insecticide and miticide containing arylalkylsilicon compounds, and process for
producing thereof. JP 61-87687.
2. Minamite, Y., T. Kanzaki, Y. Katsuda & K. Nishimoto (1990). Application of a
novel silaneophane (Hoe-498) to termiticides. Jpn. J. Environ. Entomol. Zool.
2: 117-122.
3. Rustenburg, Gb & C. J. Klaver (1991). Silafluofen, a new insecticide against
wood-boring insects and termites. International Research Group on Wood
Preservation, Doc. No. : IRG/WP/3666.
4. Nakayama, K., Y. Minamite, S. Koike, Y. Katsuda & K. Nishimoto (2001). New
application of silafluofen to termite control. International Research Group on
Wood Preservation, Doc. No. : IRG/WP/30274.
5. Yoshimura, T., Y. Katsuda & K. Nishimoto (1989). Application of molybdenum
and tungsten compounds to termiticides, 1. Termiticidal effectiveness and mode
of actions. Jpn. J. Environ. Entomol. Zool. 1: 4-12.
6. Kanzaki, T., Y. Katsuda & Y. Minamite (1994). Application of molybdenum and
tungsten compounds to termiticides. 8th Internat. Congr. Pestic Chem,
Washington, DC, Abstract Vol.2 :Poster 1D p923.
7. Umeda, M., K. Nakayama & Y. Katsuda (1997). Use of molybdate and tungstate
as termiticides, 2. Semifield test. Jpn. J. Environ. Entomol. Zool. 8: 99-104.
8. Nakayama, K., Y. Katsuda & K. Nishimoto (1998). Application of molybdenum
and tungsten compounds to bait formulations for termite control. Wood
Preservation. 24(5): 330-334.
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