Abstract
Background: The entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana have demonstrated
effectiveness against anopheline larvae in the laboratory. However, utilising these fungi for the control of
anopheline larvae under field conditions, relies on development of effective means of application as well as
reducing their sensitivity to UV radiation, high temperatures and the inevitable contact with water. This study was
conducted to develop formulations that facilitate the application of Metarhizium anisopliae and Beauveria bassiana
spores for the control of anopheline larvae, and also improve their persistence under field conditions.
Methods: Laboratory bioassays were conducted to test the ability of aqueous (0.1% Tween 80), dry (organic and
inorganic) and oil (mineral and synthetic) formulations to facilitate the spread of fungal spores over the water
surface and improve the efficacy of formulated spores against anopheline larvae as well as improve spore survival
after application. Field bioassays were then carried out to test the efficacy of the most promising formulation
under field conditions in western Kenya.
Results: When formulated in a synthetic oil (ShellSol T), fungal spores of both Metarhizium anisopliae and Beauveria
bassiana were easy to mix and apply to the water surface. This formulation was more effective against anopheline
larvae than 0.1% Tween 80, dry powders or mineral oil formulations. ShellSol T also improved the persistence of
fungal spores after application to the water. Under field conditions in Kenya, the percentage pupation of An.
gambiae was significantly reduced by 39 - 50% by the ShellSol T-formulated Metarhizium anisopliae and Beauveria
bassiana spores as compared to the effects of the application of unformulated spores.
Conclusions: ShellSol T is an effective carrier for fungal spores when targeting anopheline larvae under both
laboratory and field conditions. Entomopathogenic fungi formulated with a suitable carrier are a promising tool for
control of larval populations of malaria mosquitoes. Additional studies are required to identify the best delivery
method (where, when and how) to make use of the entomopathogenic potential of these fungi against
anopheline larvae.
Abstract
Background: The entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana have demonstrated
effectiveness against anopheline larvae in the laboratory. However, utilising these fungi for the control of
anopheline larvae under field conditions, relies on development of effective means of application as well as
reducing their sensitivity to UV radiation, high temperatures and the inevitable contact with water. This study was
conducted to develop formulations that facilitate the application of Metarhizium anisopliae and Beauveria bassiana
spores for the control of anopheline larvae, and also improve their persistence under field conditions.
Methods: Laboratory bioassays were conducted to test the ability of aqueous (0.1% Tween 80), dry (organic and
inorganic) and oil (mineral and synthetic) formulations to facilitate the spread of fungal spores over the water
surface and improve the efficacy of formulated spores against anopheline larvae as well as improve spore survival
after application. Field bioassays were then carried out to test the efficacy of the most promising formulation
under field conditions in western Kenya.
Results: When formulated in a synthetic oil (ShellSol T), fungal spores of both Metarhizium anisopliae and Beauveria
bassiana were easy to mix and apply to the water surface. This formulation was more effective against anopheline
larvae than 0.1% Tween 80, dry powders or mineral oil formulations. ShellSol T also improved the persistence of
fungal spores after application to the water. Under field conditions in Kenya, the percentage pupation of An.
gambiae was significantly reduced by 39 - 50% by the ShellSol T-formulated Metarhizium anisopliae and Beauveria
bassiana spores as compared to the effects of the application of unformulated spores.
Conclusions: ShellSol T is an effective carrier for fungal spores when targeting anopheline larvae under both
laboratory and field conditions. Entomopathogenic fungi formulated with a suitable carrier are a promising tool for
control of larval populations of malaria mosquitoes. Additional studies are required to identify the best delivery
method (where, when and how) to make use of the entomopathogenic potential of these fungi against
anopheline larvae.
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