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virginicus
(Banks) (2.7%). The study also
found an average of 9.4 colonies per
property, for a mean density of 61.8 colonies
per ha (Fig. 11.1). It was determined that the
vast majority of colonies were simple
families, i.e. headed by a single pair of
monogamous reproductives, most likely the
founding king and queen (87% in
R.
fl avipes
, 83% in
R. hageni
and 40% in
R.
virginicus
). In addition, most colonies had
limited foraging ranges, with a mean linear
foraging distance of only 4.4 m in
R. fl avipes
.
Thus in the Raleigh area, it is quite clear
that subterranean termite colonies tend to
be fairly localized but can occur in high
densities on residential properties, although
they can occur at even higher densities in
natural areas in the same region, where
densities of 125 and 300 colonies per ha
have been reported from undisturbed forest
sites (DeHeer and Vargo, 2004).
This author has also used genetic markers
to track the fate of colonies after insecticide
treatment in the fi eld such as the ability of
hexafl umuron bait (Sentricon®) to eliminate
colonies around an apartment complex in
Raleigh, North Carolina (Vargo, 2003). This
study involving 234 monitoring stations
tracked the fate of 36 subterranean termite
colonies for at least 1 year after baiting. The
study found that all of the colonies (35
R.
fl avipes
and one
R. virginicus
) disappeared
during the course of the study, demonstrating
that they were suppressed and probably
eliminated by baiting treatment. This study
also showed that termite pressure close to
the buildings decreased by more than 50%
during the 3-year sampling period. Although
there have been many studies involving
fi eld trials of hexafl umuron, the number of
colonies tracked here is far greater than any
other single study previously reported. In a
survey of 41 studies conducted up until
2003 using primarily mark-release-
recapture methods, the mean number of
colonies tracked over time per study was
3.9 (Vargo, 2003), about one-tenth the
number monitored in our study.
More recently, genetic fi ngerprinting of
colonies was used to track the fate of 62
subterranean termite colonies -
R. fl avipes
,
R. virginicus
,
R. hageni
and
C. formosanus
- baited with novifl umuron (Recruit IV®,
Dow AgroSciences) located around 24
buildings in Florida, Mississippi, Tennessee,
Louisiana and Georgia (Thoms
et al.
, 2009).
In all cases, treated colonies disappeared
from the study areas and were not detected
again. More than half the properties (54%)
had new termite activity after the fi rst bait
cycle, but DNA analysis showed that in all
cases these were new colonies that had not
been previously baited. The genetic data
provided in this study was critical for
determining that reappearance of termites
in the bait stations was not due to bait
failure but rather due to the migration of
new colonies into the areas left vacant by
successful colony elimination. These results
were instrumental in getting the bait
approved for use on new buildings in
Florida as part of the newly revised state
rules for termiticide effi cacy (Thoms
et al.
,
2009). No doubt, the use of genetic markers
in effi cacy trials will play an increasingly
important role in the registration of baits
and other termiticides.
Two studies were recently completed
examining the colony-level effect of
nonrepellent
200
Mean = 64.3
150
100
50
0
Property
Fig. 11.1.
Population densities of subterranean
termites on 19 residential properties in Raleigh,
NC. By far the most common species present was
Reticulitermes fl avipes
(89.9% of colonies),
followed by
R. hageni
(7.4% of colonies) and
R.
virginicus
(2.7%). Samples were collected from
mud tubes, in ground monitoring stations and
wood debris over a period of 6-9 months and
colony identity was determined by microsatellite
genotyping. The average size of a property was
1854 m
2
. Data from Parman and Vargo (2008).
liquid
termiticides
on
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