The Use of Plants in Vector Control - Biological and Environmental Control of Disease Vectors - page 42

4 The Use of Plants in Vector Control

Lena M. Lorenz, 1 * Marta F. Maia 1,2 and Sarah J. Moore 1,2
1 London School of Hygiene & Tropical Medicine, London, UK; 2 Ifakara Health
Institute, Bagamoyo, Tanzania

4.1 Plant-derived Chemical Control of
Disease Vectors with Plants

characterizations of natural insecticides.
Nevertheless, plants of er a wealth of novel
insect defensive strategies as a consequence of
their co-evolution with insects over the past 97
million years (Labandeira et al ., 1994) and are
being investigated in the search for new classes
of pesticides (Koch et al ., 2005) to increase the
arsenal of tools for use against insect vectors of
disease and to manage insecticide resistance to
existing insecticides.

The practice of using plant derivatives, or
botanical insecticides, dates back to the
beginning of agriculture (8000 BC) with the fi rst
documented use in China to protect rice seeds
(Dent, 2000). The agricultural revolution in
Europe in the mid-1800s depended upon crude
insecticides including rotenone, pyrethrum and
nicotine (Dayan et al ., 2009). For public health
purposes, such as the control of the vectors of
epidemic typhus, human body lice, during the
First World War, essential oils such as citronella
( Cymbopogon citratus ) mixed with mineral oil
and creosote were used (Peacock, 1916).
However, at the beginning of the 20th century,
synthetic insecticides with longer duration and
greater ei cacy became the focus of research for
the chemical control of insects.
Several thousand plants have been docu-
mented to have insecticidal activities (Rimando
and Duke, 2006), yet very few have been utilized
for agricultural or public health insect control.
Insecticides of natural origin contain a mixture
of active compounds and their concentration is
highly dependent on growth, harvest and
storage conditions. Thus, natural plant products
are dii cult to standardize, which has important
consequences when considering toxicological

4.1.1 Larvicides

Larvicides are useful to control vectors that
breed in defi ned, permanent breeding sites. A
good example is Stegomyia ( Aedes ) aegypti , the
urban vector of dengue, which breeds in
domestic water-storage containers. This mos-
quito has developed resistance to the larval
insecticides temephos and Bti ( Bacillus
thuringiensis israelensis ), and therefore new
alternative larvicides are urgently needed
(Marcombe et al ., 2011). In order to be
practicable, larvicides need to be safe to mam-
mals, fi sh and non-target invertebrates at doses
that are operationally feasible for application.
The bioactivity of plant-based larvicides depends
on the plant species, solvent used and the part of
the plant used. Conventional larvicides are

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