The Use of Plants in Vector Control - Biological and Environmental Control of Disease Vectors - page 55

contrast to fewer than fi ve anophelines per night
in Tanzania. In addition, Seyoum et al . (2003)
noted that An . funestus in western Kenya are less
sensitive to repellents (Walker et al ., 1996).
Lantana has several important qualities
that contribute to its ei cacy in preventing
mosquito house entry. It contains a variety of
terpenes and alkaloids, including high quantities
of caryophylene (Ghisalberti, 2000), which has
good repellent ei cacy against An . gambiae s.s.
(Omolo et al ., 2005). Other compounds includ-
ing eucalyptol, alpha-humelene and germ-
acrene, which are toxic to adult mosquitoes, are
also present in high quantities in the essential oil
derived from the leaves (Dua et al ., 2010).
Lantana is unusual because it emits very large
amounts of volatile organic compounds from
the leaves (Padhy and Varshney, 2005; Llusià et
al ., 2010), including -pinene, which is a known
mosquito repellent (USDA, 1947). The -pinene
emission from lantana is almost an order of
magnitude greater than that emitted from
eucalyptus, and warrants further study as it
may explain the ability of undamaged lantana
to repel mosquitoes (as opposed to most plants
requiring some mechanical damage to promote
release of repellent 'green volatiles') (Maia and
Moore, 2011). The plants used in Tanzania were
over 80 cm tall and, as such, would have emitted
a greater amount of volatile compounds than
those potted plants used in Kenya.

times more likely to transmit malaria than
mosquitoes from a sugar-poor oasis, because a
greater proportion of mosquitoes survived long
enough for the malaria parasite to develop (Gu et
al ., 2011). On the other hand, the absence of
sugar can also increase the number and fre-
quency of human blood meals as an alternative
food source (Straif and Beier, 1996), thus
increasing vectorial capacity (Beier, 1996).
In a series of papers, the ai nity of
mosquitoes and sandfl ies to sugar sources was
investigated and this life cycle requirement was
manipulated so that sugar sources were baited
with insecticides (Müller and Schlein, 2006,
2011; Schlein and Müller, 2008; Müller et al .,
2011). Müller and Schlein (2006) suggest that
desert and savannah regions with scarce
opportunities for insects to obtain sugar meals
could be ideal settings for setting up 'fl oral
centres', where the fl owers and fruit of attractive
plants are treated with insecticides (Müller and
Schlein, 2006). Alternatively, rather than using
such lure and kill strategies with a combination
of environmental and chemical control
methods, those plants that have been identifi ed
as particularly attractive to disease vectors such
as Cx . pipiens or St . albopicta could be removed or
replaced with less attractive ornamental fl owers
in order to eliminate local populations of disease
vectors (Müller et al ., 2011).
One example of such a plant that can
reduce mosquito survival is lantana (Section
4.2.3) (Gary and Foster, 2004; Impoinvil et al .,
2004). Lantana may reduce vectorial capacity
in two ways: (i) its repellent properties reduce
man-vector contact; and (ii) feeding on lantana
is not favoured by sugar-seeking mosquitoes as it
reduces survival (Impoinvil et al ., 2004) and
fecundity (Manda et al ., 2007a,b) compared to
mosquitoes that feed on other sugar sources
including domestic plants (Manda et al ., 2007b).
This negative ef ect on mosquito survival is a
highly desirable characteristic for any vector
control tool as it reduces the population size of
the vector and the probability that mosquitoes
will live long enough to transmit the malaria
parasite. Therefore, even those not using the
plant to prevent mosquitoes entering their
homes may benefi t from the 'community ef ect'
on malaria transmission. However, the
probability of mosquitoes sugar feeding on

4.2.4 Sugar resources

A novel concept of environmental control of
disease vectors is to take advantage of the main
energy source of adult insects: sugar derived
from, for example, fl owering trees and fermented
fruit (Mauer and Rowley, 1999; Müller et al .,
2011). The availability of sugar (particularly
before blood meals) infl uences lifespan, fertility
and host-seeking behaviour (Briegel, 1990;
Kaufmann and Briegel, 2004; Gary et al ., 2009)
and thus ultimately disease transmission of
many adult insects. Sugar meals may play an
important role in enhancing the ability of
mosquitoes to transmit malaria parasites by
extending female lifespan (Okech et al ., 2003).
For example, fi eld populations of An . sergentii
with better access to sugar resources were 250