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The combination of the entomopathogenic fungus Metarhizium anisopliae with the insecticide Imidacloprid increases virulence against the dengue vector Aedes aegypti (Diptera: Culicidae).

Paula AR, Carolino AT, Paula CO, Samuels RI - Parasit Vectors (2011)

Bottom Line: A sub-lethal concentration of IMI that did not significantly alter the daily survival rates or mean survival percentages of mosquitoes was identified to be 0.1 ppm.Both the combined treatment and the conidia alone were able to reduce the survival of A. aegypti compared with untreated or IMI treated mosquitoes.Importantly, mosquito survival following exposure to the combined treatment for 6 and 12 hrs was significantly reduced when compared with mosquitoes exposed to conidia alone.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Entomology and Plant Pathology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes RJ CEP 28013-602 Brazil.

ABSTRACT

Background: Dengue fever transmitted by the mosquito Aedes aegypti, is one of the most rapidly spreading insect borne diseases, stimulating the search for alternatives to current control measures. The dengue vector A. aegypti has received less attention than anophelene species, although more than 2.5 billion people are at risk of infection worldwide. Entomopathogenic fungi are emerging as potential candidates for the control of mosquitoes. Here we continue our studies on the pathogenicity of the entomopathogenic fungus Metarhizium anisopliae against adult A. aegypti females. With the aim of further reducing mean survival times of A. aegypti exposed to fungus impregnated surfaces, a sub-lethal concentration of the neonicotinoid insecticide Imidacloprid (IMI) was added to fungal suspensions.

Results: A sub-lethal concentration of IMI that did not significantly alter the daily survival rates or mean survival percentages of mosquitoes was identified to be 0.1 ppm. This sub-lethal concentration was combined with M. anisopliae conidia (1 × 10(9) conidia mL(-1)). Both the combined treatment and the conidia alone were able to reduce the survival of A. aegypti compared with untreated or IMI treated mosquitoes. Importantly, mosquito survival following exposure to the combined treatment for 6 and 12 hrs was significantly reduced when compared with mosquitoes exposed to conidia alone.

Conclusions: This is the first time that a combination of an insecticide and an entomopathogenic fungus has been tested against A. aegypti. Firstly, the study showed the potential of IMI as an alternative to the currently employed pyrethroid adulticides. Secondly, as an alternative to applications of high concentrations of chemical insecticides, we suggest that adult A. aegypti could be controlled by surface application of entomopathogenic fungi and that the efficiency of these fungi could be increased by combining the fungi with ultra-low concentrations of insecticides, resulting in higher mortality following relatively short exposure times.

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Survival curves of female Aedes aegypti exposed to five concentrations of Imidacloprid. Note: The control survival curve is the mean of all control groups (5) used for each IMI concentration. Results are the means of three experiments for each concentration of IMI tested with 30 insects used per experiment. Data points without standard error bars had errors equal to that of the previous data point.
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Figure 1: Survival curves of female Aedes aegypti exposed to five concentrations of Imidacloprid. Note: The control survival curve is the mean of all control groups (5) used for each IMI concentration. Results are the means of three experiments for each concentration of IMI tested with 30 insects used per experiment. Data points without standard error bars had errors equal to that of the previous data point.

Mentions: The sub-lethal concentration of IMI to be used in subsequent experiments was determined using the concentration-response curve of female A. aegypti. The LC50 value was 4.04 ppm (confidence limits 0.88-15.3). The concentration of IMI used was negatively correlated with survival of A. aegypti (Figure 1). The only concentration tested that did not result in significantly different survival to the untreated controls (84.6% ± 0.95) was 0.1ppm with 82.3% (± 1.97) of mosquitoes remaining alive at the end of the experiment.


The combination of the entomopathogenic fungus Metarhizium anisopliae with the insecticide Imidacloprid increases virulence against the dengue vector Aedes aegypti (Diptera: Culicidae).

Paula AR, Carolino AT, Paula CO, Samuels RI - Parasit Vectors (2011)

Survival curves of female Aedes aegypti exposed to five concentrations of Imidacloprid. Note: The control survival curve is the mean of all control groups (5) used for each IMI concentration. Results are the means of three experiments for each concentration of IMI tested with 30 insects used per experiment. Data points without standard error bars had errors equal to that of the previous data point.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3037915&req=5

Figure 1: Survival curves of female Aedes aegypti exposed to five concentrations of Imidacloprid. Note: The control survival curve is the mean of all control groups (5) used for each IMI concentration. Results are the means of three experiments for each concentration of IMI tested with 30 insects used per experiment. Data points without standard error bars had errors equal to that of the previous data point.
Mentions: The sub-lethal concentration of IMI to be used in subsequent experiments was determined using the concentration-response curve of female A. aegypti. The LC50 value was 4.04 ppm (confidence limits 0.88-15.3). The concentration of IMI used was negatively correlated with survival of A. aegypti (Figure 1). The only concentration tested that did not result in significantly different survival to the untreated controls (84.6% ± 0.95) was 0.1ppm with 82.3% (± 1.97) of mosquitoes remaining alive at the end of the experiment.

Bottom Line: A sub-lethal concentration of IMI that did not significantly alter the daily survival rates or mean survival percentages of mosquitoes was identified to be 0.1 ppm.Both the combined treatment and the conidia alone were able to reduce the survival of A. aegypti compared with untreated or IMI treated mosquitoes.Importantly, mosquito survival following exposure to the combined treatment for 6 and 12 hrs was significantly reduced when compared with mosquitoes exposed to conidia alone.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Entomology and Plant Pathology, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes RJ CEP 28013-602 Brazil.

ABSTRACT

Background: Dengue fever transmitted by the mosquito Aedes aegypti, is one of the most rapidly spreading insect borne diseases, stimulating the search for alternatives to current control measures. The dengue vector A. aegypti has received less attention than anophelene species, although more than 2.5 billion people are at risk of infection worldwide. Entomopathogenic fungi are emerging as potential candidates for the control of mosquitoes. Here we continue our studies on the pathogenicity of the entomopathogenic fungus Metarhizium anisopliae against adult A. aegypti females. With the aim of further reducing mean survival times of A. aegypti exposed to fungus impregnated surfaces, a sub-lethal concentration of the neonicotinoid insecticide Imidacloprid (IMI) was added to fungal suspensions.

Results: A sub-lethal concentration of IMI that did not significantly alter the daily survival rates or mean survival percentages of mosquitoes was identified to be 0.1 ppm. This sub-lethal concentration was combined with M. anisopliae conidia (1 × 10(9) conidia mL(-1)). Both the combined treatment and the conidia alone were able to reduce the survival of A. aegypti compared with untreated or IMI treated mosquitoes. Importantly, mosquito survival following exposure to the combined treatment for 6 and 12 hrs was significantly reduced when compared with mosquitoes exposed to conidia alone.

Conclusions: This is the first time that a combination of an insecticide and an entomopathogenic fungus has been tested against A. aegypti. Firstly, the study showed the potential of IMI as an alternative to the currently employed pyrethroid adulticides. Secondly, as an alternative to applications of high concentrations of chemical insecticides, we suggest that adult A. aegypti could be controlled by surface application of entomopathogenic fungi and that the efficiency of these fungi could be increased by combining the fungi with ultra-low concentrations of insecticides, resulting in higher mortality following relatively short exposure times.

Show MeSH
Related in: MedlinePlus