Agriculture Reference
In-Depth Information
genetic data continue to help clarify the
taxonomy of certain groups, especially
subterranean termites. Clearly, molecular
genetic tools will play an increasingly
important role in detection and management
of urban insect pests. It is important,
however, to keep in mind that such methods
do have limitations and need to be rigor-
ously verifi ed. For example, there are
private companies that now offer services to
detect bed bugs by conducting DNA analysis
using swabs of suspected areas of infestation;
however, to this author's knowledge, there
are no published reports of the accuracy
and detection limits of these methods so
caution should be exercised in using these
services until more data are available.
areas (e.g. Su and Scheffrahn, 1988).
Although this technique has been a useful
research tool, it has several limitations that
make it diffi cult to study large numbers of
colonies in the fi eld or study colonies over
an extended period of time. These
drawbacks are discussed in detail by
Parman and Vargo (2008), but briefl y,
the disadvantages of the mark-release-
recapture method are: (i) large numbers of
termites are required to effectively mark a
colony; (ii) the process of installing moni-
toring stations, collecting, marking and
recollecting termites can be time consuming
and labour intensive; (iii) there are a limited
number of dyes available; and (iv) the dyes
are short-lived so that colonies do not retain
dyes for extended periods. All of these
limitations are overcome with genetic
markers: even a few workers can be
accurately identifi ed to colony, only a single
visit to a site is required to collect samples,
genetic markers for specifi c colonies are not
lost over time, and with highly polymorphic
loci, such as microsatellites, there is almost
limitless genetic variation among colonies.
The following section will discuss two
important applications of genetic
fi ngerprinting of individual colonies: (i)
determination of colony densities and
foraging areas around structures; and (ii)
evaluation of the colony-level effects of
insecticide treatments in the fi eld.
There are few quantitative determinations
of the number of subterranean termite
colonies occurring around structures for
any specifi c geographic region. Yet such
information is critical in quantifying the
relative pressure experienced by different
areas and the risk of subterranean termite
infestation. In a recent study, large numbers
of in-ground monitors were used to deter-
mine the numbers of colonies, as well as
their locations and foraging areas, on 19
residential properties in the Raleigh, North
Carolina area (Parman and Vargo, 2008).
The study collected samples monthly for
about 9 months and, using microsatellite
markers, identifi ed 188 colonies across the
19 properties belonging to three species:
R.
fl avipes
(89.9% of all colonies),
Reticuli-
termes
hageni
(7.4%) and
Reticulitermes
Colony Identifi cation: Determination
of Colony Densities, Colony-Colony
Dynamics and Assessment of
Treatment Effi cacy
Subterranean termites are social insects that
live in colonies, yet we still have a poor
understanding of such basic features as the
number and relatedness among reproduc-
tives (kings and queens) within colonies,
the foraging ranges of colonies, and the
dynamics of colony-colony interactions.
This is because the cryptic nature of the
nesting and foraging habits of these insects
make it diffi cult to locate reproductives
within colonies and to determine the colony
identity of foragers. The application of
molecular genetic markers, especially
microsatellites, has opened up a wealth of
possibilities by permitting 'fi ngerprinting'
of colonies to infer their breeding structure,
to determine their foraging areas, estimate
population densities and to track the fate of
colonies after insecticide treatment.
In addition to advancing our understand-
ing of the basic biology of subterranean
termites, the application of genetic tools to
identify colonies has made important
contributions to termite management. For
the past 20 or more years, marking termites
using fat-soluble dyes has been the method
of choice for identifying individual colonies
in the fi eld and delimiting colony foraging
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