Agriculture Reference
In-Depth Information
Evidence of fi eld effectiveness was
summarized by Benedict and Robinson
(2003) and is limited. In 1960-1961 in
Florida 4.6 million irradiated sterile male
Ae. aegypti
were released over a 43-week
period and despite overwhelming ratios of
released to wild mosquitoes there was no
reduction in the mosquito population. In the
period between 2005 and 2009 in northern
Italy, sterile male
Ae. albopictus
released at
the rate of 896-1590 males/ha/week induced
sterility up to 70-80% and a corresponding
reduction in egg density in the ovitraps,
which was close to the calculated minimum
egg sterility value of 81% required to
suppress the local population.
The International Atomic Energy
Authority (IAEA) is pursuing projects in
Sudan for control of
An. arabiensis
and in
La Réunion for control of
Ae. albopictus
where preparatory studies on rearing
techniques, irradiation methodology, steril-
ity and mating competitiveness appear
promising but mass releases of sterile males
have not yet been reported.
any mosquito species that can be cultured
in the laboratory (D. Nimmo, UK, 2013,
personal communication).
OX513A, the lead RIDL strain of
Ae.
aegypti
, incorporates a dominant gene that
causes death of larvae and pupae in the
absence of a substantial concentration of
tetracycline. This strain is reared in the
presence of tetracycline, and male and
female pupae are separated mechanically
by size and adult males released into the
environment. Open fi eld releases of
OX513A in Grand Cayman in 2010 reduced
the native population of
Ae. aegypti
by
approximately 80% compared to control
sites over 23 weeks (Harris
et al.
, 2012). A
subsequent trial in Itaberaba, Brazil,
resulted in a similar level of reduction
within 5 months (A. McKemey, 2013,
unpublished data). In Mandacaru, Brazil, a
village of nearly 3000 people, releases
resulted in a 96% reduction of the wild
Ae. aegypti
population after 6 months
(A. McKemey, 2013, unpublished data). This
level of suppression was maintained for a
further 7 months using continued releases, at
reduced rates, to avoid re-infestation.
Insect Growth Regulators (IGRs)
IGRs might be used as sterilizing agents for
adult male mosquitoes, though mass dosing
systems would need to be developed. There
is evidence of the effectiveness of this
approach from use of targets impregnated
with IGRs for the control of various fl ies
including
Musca domestica
and
Ceratitis
capitata
(Helinski
et al
., 2009), but they
remain to be tested in mosquitoes.
Use of Bacteria
Wolbachia
is an obligate, intracellular,
maternally inherited bacterium (Brelsfoard
and Dobson, 2009) naturally present in
more than 65% of insect species (Hilgen-
boecker
et al.,
2008), including many
species of mosquito. Its application for
mosquito management would be through
the 'Incompatible Insect Technique' or
population replacement.
Release of Insects with Dominant
Lethality (RIDL)
Incompatible Insect Technique
RIDL is a form of Sterile Insect Technique
(SIT) where the sterility is caused by the
addition of a dominant lethal gene that is
conditionally expressed. It offers similar
benefi ts and issues to other SIT technologies
but overcomes the fi tness penalty caused by
irradiation. RIDL strains of various agri-
cultural insect pests and of
Ae. aegypti
and
Ae. albopictus
have been produced and the
technology could potentially be applied to
Wolbachia
has a variety of physiological
effects on its host, including 'Cytoplasmic
Incompatibility' (CI), which causes crosses
between males with one strain of
Wolbachia
and females without
Wolbachia
, or harbour-
ing a different strain, to be sterile (Brelsfoard
and Dobson, 2009).
This characteristic can be exploited as a
form of SIT known as the 'Incompatible
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