The sublethal effects of the entomopathic fungus <i>Leptolegnia chapmanii</i> on some biological parameters of the dengue vector <i>Aedes aegypti</i>

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of dengue in the Americas. The use of chemical insecticides is recommended during outbreaks of dengue in order to reduce the number of adult mosquitoes; however, because Ae. aegypti is highly synanthropic, the use of insecticides in densely populated areas is a dangerous practice. Leptolegnia chapmanii Seymour (Straminipila: Peronosporomycetes) is an entomopathogenic microorganism that has demonstrated marked pathogenicity toward the larvae of a number of mosquito species, with little or no effect on non-target insects. Therefore, the purpose of this study was to determine the sublethal effects of L. chapmanii on fecundity, number of gonotrophic cycles, fertility, and relationship between wing length and fecundity in Ae. aegypti females. Ae. aegypti females that survived infection with L. chapmanii laid fewer eggs, had a smaller number of gonotrophic cycles, had shorter wings, and were less fertile than controls. This is the first study on the sublethal effects experienced by specimens of Ae. aegypti that survived infection with zoospores of L. chapmanii. Although field studies should be carried out, the results obtained in this study are encouraging because the high and rapid larval mortality caused by L. chapmanii coupled with the reduction of reproductive capacity in Ae. aegypti females seem to cause a significant reduction in the number of adults in the mid and long term, thereby reducing the health risks associated with Ae. aegypti.Centro de Estudios Parasitológicos y de VectoresInstituto de Botánica "Dr. Carlos Spegazzini

Neotropical Seasonally Dry Forests: Response of Soil Fungal Communities to Anthropogenic Actions

The aim of this review was to analyze the information available on soil fungal community of Neotropical Seasonally dry forests, with special attention given to the Chaco area. This review is focused on the loss of soil fungal community due to anthropogenic actions such as forest clearing. Over the last decades, the expansion of the agricultural frontier has had a wide range of physical, chemical and biological effects on Neotropical dry forests. As these changes on the Schinopsis dry forests (Chaco) have rendered the ecosystem vulnerable, these areas have become some of the few protected areas in South America. After analyzing both national and international studies to find the latest research available on the topic we have noticed there is lack of specific studies on soil fungal community in the Chaco area, unlike Cerrado and Caatinga where most studies have been carried out. Therefore, we propose to conduct more in-depth studies on soil fungi in Schinopsis forests to revalue the Chaco fungal community to use them as potential indicators of soil health and to develop new management techniques.Instituto de Botánica "Dr. Carlos Spegazzini

The sublethal effects of the entomopathic fungus <i>Leptolegnia chapmanii</i> on some biological parameters of the dengue vector <i>Aedes aegypti</i>

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of dengue in the Americas. The use of chemical insecticides is recommended during outbreaks of dengue in order to reduce the number of adult mosquitoes; however, because Ae. aegypti is highly synanthropic, the use of insecticides in densely populated areas is a dangerous practice. Leptolegnia chapmanii Seymour (Straminipila: Peronosporomycetes) is an entomopathogenic microorganism that has demonstrated marked pathogenicity toward the larvae of a number of mosquito species, with little or no effect on non-target insects. Therefore, the purpose of this study was to determine the sublethal effects of L. chapmanii on fecundity, number of gonotrophic cycles, fertility, and relationship between wing length and fecundity in Ae. aegypti females. Ae. aegypti females that survived infection with L. chapmanii laid fewer eggs, had a smaller number of gonotrophic cycles, had shorter wings, and were less fertile than controls. This is the first study on the sublethal effects experienced by specimens of Ae. aegypti that survived infection with zoospores of L. chapmanii. Although field studies should be carried out, the results obtained in this study are encouraging because the high and rapid larval mortality caused by L. chapmanii coupled with the reduction of reproductive capacity in Ae. aegypti females seem to cause a significant reduction in the number of adults in the mid and long term, thereby reducing the health risks associated with Ae. aegypti.Centro de Estudios Parasitológicos y de VectoresInstituto de Botánica "Dr. Carlos Spegazzini

Neotropical Seasonally Dry Forests: Response of Soil Fungal Communities to Anthropogenic Actions

The aim of this review was to analyze the information available on soil fungal community of Neotropical Seasonally dry forests, with special attention given to the Chaco area. This review is focused on the loss of soil fungal community due to anthropogenic actions such as forest clearing. Over the last decades, the expansion of the agricultural frontier has had a wide range of physical, chemical and biological effects on Neotropical dry forests. As these changes on the Schinopsis dry forests (Chaco) have rendered the ecosystem vulnerable, these areas have become some of the few protected areas in South America. After analyzing both national and international studies to find the latest research available on the topic we have noticed there is lack of specific studies on soil fungal community in the Chaco area, unlike Cerrado and Caatinga where most studies have been carried out. Therefore, we propose to conduct more in-depth studies on soil fungi in Schinopsis forests to revalue the Chaco fungal community to use them as potential indicators of soil health and to develop new management techniques.Instituto de Botánica "Dr. Carlos Spegazzini

The sublethal effects of the entomopathic fungus <i>Leptolegnia chapmanii</i> on some biological parameters of the dengue vector <i>Aedes aegypti</i>

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of dengue in the Americas. The use of chemical insecticides is recommended during outbreaks of dengue in order to reduce the number of adult mosquitoes; however, because Ae. aegypti is highly synanthropic, the use of insecticides in densely populated areas is a dangerous practice. Leptolegnia chapmanii Seymour (Straminipila: Peronosporomycetes) is an entomopathogenic microorganism that has demonstrated marked pathogenicity toward the larvae of a number of mosquito species, with little or no effect on non-target insects. Therefore, the purpose of this study was to determine the sublethal effects of L. chapmanii on fecundity, number of gonotrophic cycles, fertility, and relationship between wing length and fecundity in Ae. aegypti females. Ae. aegypti females that survived infection with L. chapmanii laid fewer eggs, had a smaller number of gonotrophic cycles, had shorter wings, and were less fertile than controls. This is the first study on the sublethal effects experienced by specimens of Ae. aegypti that survived infection with zoospores of L. chapmanii. Although field studies should be carried out, the results obtained in this study are encouraging because the high and rapid larval mortality caused by L. chapmanii coupled with the reduction of reproductive capacity in Ae. aegypti females seem to cause a significant reduction in the number of adults in the mid and long term, thereby reducing the health risks associated with Ae. aegypti.Centro de Estudios Parasitológicos y de VectoresInstituto de Botánica "Dr. Carlos Spegazzini

First record of <i>Fusarium verticillioides</i> as an entomopathogenic fungus of grasshoppers

Fusarium verticillioides (Saccardo) Nirenberg (Ascomycota: Hypocreales) is the most common fungus reported on infected corn kernels and vegetative tissues, but has not yet been documented as being entomopathogenic for grasshoppers. Grasshoppers and locusts represent a large group of insects that cause economic damage to forage and crops. Tropidacris collaris (Stoll) (Orthoptera: Acridoidea: Romaleidae) is a large and voracious grasshopper that in recent years has become an increasingly recurrent and widespread pest in progressively more greatly extended areas of some of in Argentina's northern provinces, with chemical insecticides being currently the only means of control. During February and March of 2008-09, nymphs and adults of T. collaris were collected with sweep nets in dense woodland vegetation at a site near Tres Estacas in western Chaco Province, Argentina, and kept in screened cages. F. verticillioides was isolated from insects that died within 10 days and was cultured in PGA medium. Pathogenicity tests were conducted and positive results recorded. Using traditional and molecular-biological methods, an isolate of F. verticillioides was obtained from T. collaris, and its pathogenecity in the laboratory was shown against another harmful grasshopper, Ronderosia bergi (Stål) (Acridoidea: Acrididae: Melanoplinae). The mortality caused by F. verticillioides on R. bergi reached 58 ± 6.53% by 10 days after inoculation. This is the first record of natural infection caused by F. verticillioides in grasshoppers.Instituto de Botánica "Dr. Carlos Spegazzini

First record of <i>Fusarium verticillioides</i> as an entomopathogenic fungus of grasshoppers

Fusarium verticillioides (Saccardo) Nirenberg (Ascomycota: Hypocreales) is the most common fungus reported on infected corn kernels and vegetative tissues, but has not yet been documented as being entomopathogenic for grasshoppers. Grasshoppers and locusts represent a large group of insects that cause economic damage to forage and crops. Tropidacris collaris (Stoll) (Orthoptera: Acridoidea: Romaleidae) is a large and voracious grasshopper that in recent years has become an increasingly recurrent and widespread pest in progressively more greatly extended areas of some of in Argentina's northern provinces, with chemical insecticides being currently the only means of control. During February and March of 2008-09, nymphs and adults of T. collaris were collected with sweep nets in dense woodland vegetation at a site near Tres Estacas in western Chaco Province, Argentina, and kept in screened cages. F. verticillioides was isolated from insects that died within 10 days and was cultured in PGA medium. Pathogenicity tests were conducted and positive results recorded. Using traditional and molecular-biological methods, an isolate of F. verticillioides was obtained from T. collaris, and its pathogenecity in the laboratory was shown against another harmful grasshopper, Ronderosia bergi (Stål) (Acridoidea: Acrididae: Melanoplinae). The mortality caused by F. verticillioides on R. bergi reached 58 ± 6.53% by 10 days after inoculation. This is the first record of natural infection caused by F. verticillioides in grasshoppers.Instituto de Botánica "Dr. Carlos Spegazzini

Compatibility of chemical insecticides and entomopathogenic fungi for control of soybean defoliating pest, Rachiplusia nu.

Fil: Pelizza, Sebastián Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios en Parasitología y Vectores; ArgentinaFil: Schalamuk, Santiago. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica; ArgentinaFil: Simón, María Rosa. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Stenglein, Sebastián Alberto. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía. Laboratorio de Biología Funcional y Biotecnología. Azul; ArgentinaFil: Pacheco Marino, Suani Giovanna. Instituto de Genética Veterinaria Ingeniero Fernando Noel Dulout. La Plata; ArgentinaFil: Scorsetti, Ana Clara. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Botánica Carlos Spegazzini; Argentin

Pathogenic and enzyme activities of the entomopathogenic fungus <i>Tolypocladium cylindrosporum</i> (Ascomycota: Hypocreales) from Tierra del Fuego, Argentina

Tolypocladium cylindrosporum is an entomopathogenic fungi that has been studied as a biological control agent against insects of several orders. The fungus has been isolated from the soil as well as from insects of the orders Coleoptera, Lepidoptera, Diptera and Hymenoptera. In this study, we analyzed the ability of a strain of T. cylindrosporum, isolated from soil samples taken in Tierra del Fuego, Argentina, to produce hydrolytic enzymes, and to study the relationship of those activities to the fungus pathogenicity against pest aphids. We have made the traditional and molecular characterization of this strain of T. cylindrosporum. The expression of hydrolase activity in the fungal strain was estimated at three incubation temperatures (4ºC, 12ºC and 24ºC), on different agar media supplemented with the following specific substrates: chitin azure, Tween ® 20, casein, and urea for chitinase, lipase, protease, and urease activity, respectively. The hydrolytic-enzyme activity was estimated qualitatively according to the presence of a halo of clarification through hydrolase action, besides was expressed semi-quantitatively as the ratio between the hydrolytic-halo and colony diameters. The pathogenicity of the fungus was tested on adults of the aphid Rhopalosiphum padi at three temperatures of incubation (4ºC, 12ºC and 24ºC). The suspension was adjusted to a concentration of 1x10 7 conidia/ml. In pathogenicity assays at seven days post-inoculation, the fungus caused the mortality of adults of Ropalosiphum padi at different temperatures also showed a broad ability to grow on several agar-culture media, supplemented with different carbon sources at the three incubation temperatures tested. Although, the growth was greater with higher incubation temperatures (with maximum levels at 24°C), the fungus reached similar colony diameters after 15 days of incubation on the medium supplemented with Tween® 20 at the lower two incubation temperatures of 4°C or 12°C. In accordance with the results on colony diameters, the fungus revealed an ability to degrade casein, chitin derivatives, Tween® 20, and urea as evidenced by the appearance of a halo around the fungal colony. Because of its origin and temperature tolerance, this Argentine strain has great potential for use as a biocontrol agent for insect pest control in cold and temperate environments.Facultad de Ciencias Agrarias y Forestale

Laboratory test of Beauveria bassiana (Balsamo‑Crivelli) Vuillemin s.l. (Hypocreales: Clavicipitaceae) baits for the biocontrol of the Toad grasshopper pest, Bufonacris claraziana (Saussure) (Orthoptera: Tristiridae)

Background: The Toad grasshopper pest, Bufonacris claraziana (Saussure) (Orthoptera: Tristiridae) is an endemic species of the Argentine Patagonia region. Among the Tristiridae family, it is the only species recognized as harmful to agricultural and livestock activities in the country. Outbreaks of B. claraziana have become a recurring phenomenon in the recent years, affecting different areas of the Patagonian provinces. The aim of this study was to evaluate, as laboratory bioassays, the mortality in young nymphs of this species treated with bait formulations of the entomopathogenic fungus Beauveria bassiana (Hypocreales: Clavicipitaceae). Results: The two treatments performed, one of them (I) with conidia of B. bassiana only and the other (II) with conidia of B. bassiana plus canola oil as phagostimulant, produced significantly higher mortality than the control (p < 0.05). At 10 days from the start of the bioassay, the mortality registered in the treatment II (53.33%) was higher than that in the treatment I (23.33%) (p < 0.05). This difference was similar at 15 days post-treatment, mortality reached in treatment II (93.33%) higher than in treatment I (73.33%). Conclusions: Results demonstrated that the combination of canola oil with wheat bran makes the bait with conidia of B. bassiana more attractive for nymphs of B. claraziana, enhancing mortality over a shorter interval of time.Centro de Estudios Parasitológicos y de VectoresInstituto de Botánica "Dr. Carlos Spegazzini