BackgroundResistance to chemical insecticides plus high morbidity rates have lead to rising interest in fungi as candidates for biocontrol agents of mosquito vectors. In most studies fungal infections have been induced by exposure of mosquitoes to various surfaces treated with conidia. In the present study eight Mexican strains of Beauveria bassiana were assessed against Aedes aegypti by direct exposure of females to 6 × 108 conidia ml -1 on a filter paper, afterwards, the transmission of the least and most virulent isolates was evaluated by mating behavior from virgin, fungus-contaminated male to females, to examine this ethological pattern as a new approach to deliver conidia against the dengue vector.MethodsIn an exposure chamber with a filter paper impregnated with 6 × 108 conidia ml -1 of the least and most virulent strains of B. bassiana, 6-8 day old males of A. aegypti were exposed for 48 hours, and then transferred individually (each one was a replicate) to another chamber and confined with twenty healthy females of the same age. Clean males were used in controls. Survival, infection by true mating (insemination) or by mating attempts (no insemination) and fecundity were daily registered until the death of last female. Data analysis was conducted with proc glm for unbalanced experiments and means were separated with the Ryan test with SAS.ResultsAll strains were highly virulent with LT50 ranging from 2.70 (± 0.29) to 5.33 (± 0.53) days. However the most (Bb-CBG2) and least virulent (Bb-CBG4) isolates were also transmitted by mating behavior; both killed 78-90% of females in 15 days after being confined with males that had previously been exposed for 48 hours to fungi. Of these mortality rates, 23 and 38% respectively, were infections acquired by copulations where insemination occurred. The LT50 for sexually-infected females were 7.92 (± 0.46) and 8.82 (± 0.45) days for both strains, while the one in control was 13.92 (± 0.58). Likewise, fecundity decreased by 95% and 60% for both Bb-CBG2 and Bb-CBG4 isolates in comparison with control. The role of mating attempts in this delivery procedure of B. bassiana is discussed.ConclusionsThis is the first report about transmission of B. bassiana by mating behavior from virgin, fungus-contaminated males to females in A. aegypti. Fungal infections acquired by this route (autodissemination) infringed high mortality rates (90%) in mated or approached females. However, prior to releasing virgin, fungus-contaminated males to spread B. basasiana among females of A. aegypti, this novel alternative needs further investigations.

BackgroundDengue is a viral disease transmitted by Aedes mosquitoes. It is a threat for public health worldwide and its primary vector Aedes aegypti is becoming resistant to chemical insecticides. These factors have encouraged studies to evaluate entomopathogenic fungi against the vector. Here we evaluated mortality, infection, insemination and fecundity rates in A. aegypti females after infection by autodissemination with two Mexican strains of Metarhizium anisopliae.MethodsTwo M. anisopliae strains were tested: The Ma-CBG-1 least virulent (lv), and the Ma-CBG-2 highly virulent (hv) strain. The lv was tested as non mosquito-passed (NMP), and mosquito-passed (MP), while the hv was examined only as MP version, therefore including the control four treatments were used. In the first bioassay virulence of fungal strains towards female mosquitoes was determined by indirect exposure for 48 hours to conidia-impregnated paper. In the second bioassay autodissemination of fungal conidia from fungus-contaminated males to females was evaluated. Daily mortality allowed computation of survival curves and calculation of the LT50 by the Kaplan-Meier model. All combinations of fungal sporulation and mating insemination across the four treatments were analyzed by χ2. The mean fecundity was analyzed by ANOVA and means contrasted with the Ryan test.ResultsIndirect exposure to conidia allowed a faster rate of mortality, but exposure to a fungal-contaminated male was also an effective method of infecting female mosquitoes. All females confined with the hv strain-contaminated male died in fifteen days with a LT50 of 7.57 (± 0.45) where the control was 24.82 (± 0.92). For the lv strain, it was possible to increase fungal virulence by passing the strain through mosquitoes. 85% of females exposed to hv-contaminated males became infected and of them just 10% were inseminated; control insemination was 46%. The hv strain reduced fecundity by up to 99%, and the lv strain caused a 40% reduction in fecundity.ConclusionsThe hv isolate infringed a high mortality, allowed a low rate of insemination, and reduced fecundity to nearly zero in females confined with a fungus-contaminated male. This pathogenic impact exerted through sexual transmission makes the hv strain of M. anisopliae worthy of further research.

BackgroundDengue is the most prevalent arboviral disease transmitted by Aedes aegypti worldwide, whose chemical control is difficult, expensive, and of inconsistent efficacy. Releases of Metarhizium anisopliae—exposed Ae. aegypti males to disseminate conidia among female mosquitoes by mating represents a promising biological control approach against this important vector. A better understanding of fungus virulence and impact on reproductive parameters of Ae. aegypti, is need before testing auto-dissemination strategies.Methodology/Principal FindingsMortality, mating competitiveness, sperm production, and the capacity to auto-disseminate the fungus to females up to the 5thcopulation, were compared between Aedes aegypti males exposed to 5.96 x 107 conidia per cm2 of M. anisopliae and uninfected males. Half (50%) of fungus-exposed males (FEMs) died within the first 4 days post-exposure (PE). FEMs required 34% more time to successively copulate with 5 females (165 ± 3 minutes) than uninfected males (109 ± 3 minutes). Additionally, fungus infection reduced the sperm production by 87% at 5 days PE. Some beneficial impacts were observed, FEMs were able to successfully compete with uninfected males in cages, inseminating an equivalent number of females (about 25%). Under semi-field conditions, the ability of FEMs to search for and inseminate females was also equivalent to uninfected males (both inseminating about 40% females); but for the remaining females that were not inseminated, evidence of tarsal contact (transfer of fluorescent dust) was significantly greater in FEMs compared to controls. The estimated conidia load of a female exposed on the 5th copulation was 5,200 mL-1 which was sufficient to cause mortality.Conclusion/SignificanceOur study is the first to demonstrate auto-dissemination of M. anisopliae through transfer of fungus from males to female Ae. aegypti during mating under semi-field conditions. Our results suggest that auto-dissemination studies using releases of FEMs inside households could successfully infect wild Ae. aegypti females, providing another viable biological control tool for this important the dengue vector.

ResumenEl huitlacoche posee características nutrimentales como altos niveles de fibra dietaria, proteínas, aminoácidos, oligosacáridos, ácidos grasos esenciales, vitaminas, minerales y compuestos fenólicos, lo que hace que pueda aportar un beneficio importante a la nutrición. Esta investigación tuvo como objetivo evaluar la producción natural del huitlacoche en el estado de Aguascalientes, México. Se evaluaron siete municipios donde los muestreos se realizaron completamente al azar por conveniencia con una superficie de 500 m 2 por hectárea para cada tratamiento, los datos se obtuvieron cuando el elote estaba a punto de ser cosechado y el hongo alcanzó el desarrollo de las agallas para los muestreos denominados tratamientos. Las variables evaluadas fueron: índice de severidad (IS), porcentaje de incidencia (PI), gramos de huitlacoche por mazorca infectada (GMI) y rendimiento por hectárea (RH). Los resultados se analizaron mediante un análisis de varianza, prueba de Tukey (p= 0.05) y correlación lineal de Pearson. El tratamiento 3 (semilla criolla amarilla de temporal) en la localidad del Ejido de Peñuelas en el Municipio de Aguascalientes, fue el mejor y significativamente diferente a todos los demás tratamientos, ya que obtuvo el mayor rendimiento por hectárea (90.554 kg AbstractThe corn smut has nutritional characteristics as high levels of dietary fiber, protein, amino acids, oligosaccharides, essential fatty acids, vitamins, minerals and phenolic compounds, which makes it can bring significant benefit to nutrition. This research aimed to evaluate the natural production of corn smut in the state of Aguascalientes, Mexico. Seven municipalities where the samples are completely made randomly by convenience with an area of 500 m 2 per hectare for each treatment, data were obtained when the corn was about to be harvested and the fungus reached the development of guts for evaluated sampling known treatments. The variables evaluated were: severity index (IS), percentage of incidence (PI), grams per infected ear of corn smut (GMI) and yield per hectare (RH). The results were analyzed by analysis of variance, Tukey test (p= 0.05) and Pearson linear correlation. The treatment 3 (yellow native seed temporary) in the village of Ejido Peñuelas in the Municipality of Aguascalientes, was the best and significantly different from all other treatments, as obtained the highest yield per hectare (90.554 kg ha -1 ) and he presented a greater severity index infected ears (18.67%). Native seeds showed higher production of corn smut. ha-1 ) y presentó un mayor índice de severidad por mazorcas infectadas (18.67%). Las semillas criollas presentaron mayor producción de huitlacoche.Palabras clave: carbón común del maíz, incidencia, riego, severidad, temporal. IntroducciónHuitlacoche es el nombre que se le da a las agallas o tumores que se forman en plantas de maíz (Zea mays ssp. mays) y teozintle (Zea mays ssp. parviglumis) por la acción del hongo Ustilago maydis. La producción de este hongo no es planificada para el cultivo, se produ...

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