Control of Disease Vectors using Fungi - Biological and Environmental Control of Disease Vectors - page 86

the impact on mosquito survival (Scholte et al. ,
2005). This disparity in progress may be
attributed to the profi t-driven nature of
commercial agriculture, but may also be due to
the only recent discovery of vector-specifi c
fungal isolates that can be produced on a large
scale, in formulations that allow for easy
application against adult mosquitoes.
Considerable progress has been made in the last
10 years towards developing fungi for adult
malaria mosquito control, with some novel
ef ective ways to deliver fungi (Lwetoijera et al. ,
2010; Mnyone et al. , 2012); however, optimizing
coverage so that impacts on whole vector
populations and malaria morbidity and
mortality can be demonstrated has yet to be
realized. Progress from the bench to large-scale
studies similar to those staged in the mid-1990s
for insecticide-treated bed nets (Lengeler, 2004)
is crucial in determining success in the fi eld.
As well as ef ective delivery systems,
formulations must be developed that allow for
extended persistence of fungal spores in the
environment. Regular retreatment of targets or
walls may render the technology economically
unfeasible. More studies are required to
determine residual activity of spores in dif erent
delivery systems in the fi eld and to develop
formulations that can match the persistence of
chemicals used for vector control today.
Sole use of fungal formulations may not
provide adequate coverage to stop transmission.

As fungal applications appear to be compatible
with chemical insecticides (Ramaraje Urs et al. ,
1967; Kaaya et al. , 1996; Purwar and Sachan,
2006), mosaics or rotations between chemical
and fungal control could be employed and may
feasibly slow development of resistance to one or
both. In experimental hut trials, combinations
of fungal-impregnated net curtains and
permethrin-treated bed nets reduced blood-
feeding of pyrethroid-resistant Cx . quinque-
fasciatus (Howard et al. , 2010b), highlighting the
possibility of employing fungal and chemical
rotations. Fungal applications may have the
potential to 'rescue' chemicals where they have
already failed and combinations of fungal and
chemical insecticides can have synergistic ef ects
against insects (Purwar and Sachan, 2006).
Fungal exposure may even render insecticide-
resistant insects once more susceptible (Purwar
and Sachan, 2006; Farenhorst et al. , 2010).
As research becomes more focused on
resistance management, integrated vector
management (IVM) approaches (WHO, 2008)
are likely to be crucial in promoting ef ectiveness
and sustainability of vector control methods.
There are still key biological issues to be
addressed and technological developments to be
made before fungal biopesticides can become a
mainstream vector control tool, but at present
the prospects for fungal control look promising
and may have a prominent role to play in IVM
strategies in the future of mosquito control.

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