Agriculture Reference
In-Depth Information
• Ovitraps are an established tool for
monitoring mosquitoes. The core weak-
ness of ovitraps for control is that they
only kill the aquatic stages and not the
adults who lay these eggs and hence they
have only a limited impact on the
numbers of eggs laid in natural oviposi-
tion sites. As mosquito larval survival is
generally low and density dependent
(Walsh, 2011), in many situations ovit-
raps may have a very limited impact on
the overall rate of adult emergence.
• Adult traps catch mosquitoes but the
question remains over whether they will
be able to reduce mosquito abundance
suffi ciently to have an impact on disease
transmission. Their utility may be
enhanced by outdoor placement and use
in a push-pull strategy where repellents
act indoors to provide protection and
drive more mosquitoes into the traps.
• Sugar baits generally seem unsuitable for
use in areas with fl owering vegetation
and there is a question over their suita-
bility in cities where abundant blood
hosts are readily available. Stone
et al.
(2012), however, found that emerging
female
Anopheles gambiae
will feed fi rst
on sugar if a blood meal is not available
and so sugar baits could work well in
conjunction with mosquito nets.
• Insecticidal paints are likely to be signif-
icantly more labour intensive to apply
than indoor residual insecticide sprays
and, with the addition of their decora-
tive benefi ts, they are more likely to be
channelled through the private sector for
individual householders than incorpo-
rated in mosquito management opera-
tions.
• Entomopathogenic fungi are relatively
short-lived on surfaces and there is a
need to develop formulation and deliv-
ery systems suitable for mosquito control
programmes (Bukhari
et al.
, 2011).
• The pick-up of entomopathogenic fungi,
IGRs or other control agents from auto-
dissemination systems may be enhanced
by trap design and formulation, for
example through use of magnetic
(Magthanite
TM
) or electrostatic ('Ento-
stat')
powders.
• No nematode product for control of
mosquitoes is now commercially availa-
ble and the technology suffers a number
of disadvantages. A review of the popu-
lation dynamics of the host-parasite
interaction led Hominick and Tingley
(1984) to conclude that mermithid popu-
lations are controlled by such tight
density-dependent constraints that they
can cause at most only moderate depres-
sions of their host populations. They
considered that single inoculative
releases of mermithids would be unlikely
to provide effective long-term control of
mosquitoes. Mermithids also demon-
strate poor reliability of control and sus-
ceptibility to environmental conditions.
Petersen (1982) reviewed entomogenous
nematodes from other families and
concluded that they will remain 'on the
shelf' until the need for such biological
control provides businesses with the
incentive to make them available for
general use.
• Marten and Reid (2007) claimed that
virtually all published instances of mos-
quito elimination in recent years have
involved use of copepods. The potential
to extend their use for local elimination
of
Ae. aegypti
and
Ae. albopictus
depends on the existence of relatively
permanent container breeding habitats,
the professional capacity for copepod
management and supportive community
participation with acceptance of main-
taining copepods in any open water stor-
age tanks.
• A key challenge in the use of mosquito
densoviruses involves the production of
sufficient quantities for field application,
requiring large-scale mosquito rearing or
large-scale cell culture.
• Although the RIDL gene is self-limiting
and its environmental impact benign,
the approach is a genetically modifi ed
(GM) technology and as such it attracts
criticism from some anti-GM pressure
groups and regulatory scrutiny could be
harder.
• Public and regulatory perception of
Wolbachia
benefi ts from the fact that it is
a natural organism and transinfection
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