The effectiveness of Metarhizium anisopliae IP 46 conidia mixed with soil was tested against Aedes aegypti eggs. Mycelium and new conidia developed first on eggs between 4.8 and 15 days respectively after incubation of fungus-treated soils at 3.3 × 10(3) up to 3.3 × 10(5) conidia/g soil at 25°C and relative humidities close to saturation. After 15-day incubation, 53.3% of the eggs exposed to soil with 3.3 × 10(5) conidia/g showed external development of mycelium and conidia. Fungus-inoculated soils (but not untreated controls) showed some mycelial growth and sporulation apart from the eggs. Some eggs on treated soils hatched; those larvae died and eventually showed fungal development on their bodies. The cumulative relative eclosion of larvae after submersion of treated eggs in water decreased from 52.2% at 3.3 × 10(3) conidia/g to 25.3% at 3.3 × 10(5) conidia/g. These findings clearly showed that A. aegypti eggs can be infected by M. anisopliae when deposited on fungus-contaminated soil. The effectiveness of M. anisopliae against gravid females, larvae, and also eggs of A. aegypti underscored the possible usefulness of this fungus as a mycoinsecticide, whether naturally occurring or artificially applied, in the breeding sites of this mosquito.
The pathogenicity of 19 hypocrealean entomopathogenic fungi from seven different genera in adult Aedes aegypti was tested. All fungi proved to be pathogenic, and Isaria fumosorosea, Lecanicillium muscarium, Lecanicillium psalliotae, Metarhizium anisopliae, Metarhizium lepidiotae, Metarhizium majus, Metarhizium frigidum, Paecilomyces carneus, and Paecilomyces lilacinus caused total mortality within 15 days of exposure of mosquitoes to the fungal culture. All fungi developed on dead individuals. The high susceptibility of adults to most tested strains underlines the interest of entomopathogenic fungi-especially those of the genera Metarhizium, Isaria, Paecilomyces and Lecanicillium--for biological control of A. aegypti.
The larvicidal potential of the crude ethanolic extracts (CEE) of the stem peel of Sapindus saponaria was evaluated against Rhipicephalus sanguineus. Lethal concentrations (LC), were calculated by preparing CEE solutions at different concentrations in distilled water. Larvae fasted for 14-21 days were utilized in the bioassays, after incubation of engorged females collected from infested environments frequented by dogs in several neighborhoods of Goiânia, GO. Bioassays were performed in a specially constructed biological chamber for testing botanical acaricides, acclimatized to 27±1ºC, RH>80%. The larvae were counted on filter paper envelopes impregnated with the solutions or distilled water and larval mortality observed after 48h. S. saponaria showed good larvicidal activity (LC50 and LC99 of 1994 and 3922ppm, respectively) and the results demonstrated its potential as a botanical acaricide and an alternative control measure for R. sanguineus.
Significant progress in developing Leptolegnia chapmanii as a biological control agent against mosquitoes will be accelerated by improved and simpler methods to detect and to isolate this virulent and rapidly lethal watermold from field-collected mosquito larvae. To date, however, this oomycete has remained understudied and little used. This study presents a simplified method to detect Leptolegnia in infected Aedes aegypti larvae. The development of L. chapmanii inside mosquitoes is easily monitored when pathogen-treated larvae are quasi-immobilized for an initial 48 h in the water film on plates of water agar amended with antibiotic (chloramphenicol, 0.5-1 g/L) and fungicide (thiabendazole, 4-8 g/L) and then transferred to a larger volume of water for an additional 48 h. Surprisingly, chloramphenicol stimulated oosporogenesis by L. chapmanii. The method permits processing of large numbers of A. aegypti and other culicid larvae and is useful for both obtaining new strains and also monitoring the efficacy of L. chapmanii during field tests.
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