Simulated Field Evaluation of Six Techniques for Controlling
the
Drywood Termite Incisitermes minor (Isoptera: Kalotermitidae)
in Residences
ABSTRACT Nonchemical and chemical methods
for control of drywood
termites were evaluated under simulated field conditions. Specifically,
we
assessed the efficacy of four methods currently marketed as alternatives
to
whole-structure fumigation for control of drywood termites: excessive
heat,
excessive cold, electrocution, and microwaves. In addition, we evaluated
a
reduced dosage of methyl bromide synergized with carbon dioxide, as
well as
a standard fumigation treatment with sulfuryl fluoride.
Tests were conducted using Incisitermes minor (Hagen) in
artificially infested or naturally infested boards of various dimensions
used in construction. Infested boards were placed into the attic,
drywalls, or subarea of the Villa Termiti, a symmetrical building
constructed specifically for these tests. Commercial pest control
operators performed 5 of the 6 control methods; liquid nitrogen was
applied
by University of California personnel. For artificially infested boards,
mortality was measured 3-d and 4-wk post-treatment. For naturally infested
boards, mortality was evaluated only 4-wk post-treatment. Efficacy
performance of all treatments was compared to 90, 95, and 99 percent
levels
of mortality.
Termite mortality in artificial boards was 100 percent at 3-d and
4-wk post-treatment for both fumigant gases. Heating the whole-structure
or spot-applications using microwaves resulted in 96 and 90 percent
mortality, respectively, 3-d post-treatment. Mortality levels 4-wk
post-treatment increased to 98 percent for heating and 92 percent for
microwaves. Spot-applications of liquid nitrogen at the 30-min@1.4
kg/min
dose (highest dose tested) achieved 100 percent mortality 3-d
post-treatment. However, for the 15-min@ 0.9 kg/min and 7-min@ 0.9
kg/min
dosages, 4-wk post-treatment mortality levels were 99 percent and 87
percent, respectively. Mortality by electrocution of termites in
artificially infested boards was 44 percent 3-d post-treatment in the
first
test. Four-weeks post-treatment drywood termite mortality increased
to 82
percent. In a second electrocution test, using spot-application techniques
infrequently used in structures, mortality levels increased to 93 percent
3-d and 98 percent 4-wk post-treatment.
For naturally infested boards, both fumigants exceeded the 99
percent level of mortality. Nonchemical applications of heat for
whole-structure and spot-applications with microwaves resulted in 100
percent and 99 percent mortality levels for naturally infested boards.
Chemical applications of liquid nitrogen were at or near 100 percent
for
naturally infested boards tested at the 30-min@1.4 kg/min and 15-min@0.9
kg/min dosages. However, mortality was significantly lower (74 percent)
for the 7-min@0.9 kg/min dose. Mortality levels from electrocution
were 89
percent and 95 percent 4-wk post-treatment, respectively, in the two
tests.
The distribution of termite survivors varied for some techniques by
: 1) location within the test structure and 2) galleries within test
boards. Visual signs of damage to test boards, drywall, and the Villa
Termiti were noted for some treatment techniques. This study provides
information for evaluation of the relative efficacy of nonchemical
alternatives and fumigation technology for the eradication/elimination
of
drywood termite infestations in structures.