Activity of oil-formulated Beauveria bassiana against Triatoma sordida in peridomestic areas in central Brazil

Field tests were carried out during the rainy season of 2001/2002 in São Luís de Montes Belos, Goiás, Brazil, to evaluate the potential of the entomopathogenic fungus, Beauveria bassiana, against peridomestic Triatoma sordida. An oil-water formulation of the isolate CG 14 (Embrapa) was applied in triatomine infested hen houses of four farms at a final concentration of 10(6) conidia/cm². Numbers of T. sordida decreased over the next 25 days, after application of the fungus, and B. bassiana developed on dead insects in one hen house. A high number of B. bassiana colonies was detected in substrates collected in treated hen houses 24 h after application of CG 14. In the following three months the presenceof B. bassiana declined to values found before treatment

Calcium Regulated Appresorium Formation of the Entomopathogenic Fungus Zoophthora Radicans

The fungusZoophthora radicans (Zygomycetes: EntomophthoraThe fungusZoophthora radicans (Zygomycetes: Entomophthorales) requires external Ca2+ for appressorium formation but not for conidial germination. The number of appressoria formed depends on the Ca2+ concentration of the medium. At low [Ca2+] (100 pM) nuclear division and germ tube growth are significantly reduced compared to higher Ca2+ concentrations (10 and 1,000 μM). By contrast, neither external K+ nor external Cl− is needed for germination or appressorium formation. Treatment of conidia with a Ca2+-antagonist, Nd3+, and a Ca2+-channel blocker, nifedipine, inhibits appressorium formation, showing that a Ca2+ influx is required for appressorium formation. Furthermore, the partial yet saturating inhibition by nifedipine and complete inhibition by Nd3+ indicates that at least two kinds of Ca2+ channels are involved in appressorium formation. A contribution of intracellular Ca2+ to the signal transduction chain for the formation of appressoria is demonstrated by the inhibitory effect of the intracellular Ca2+ antagonist TMB-8. The calmodulin antagonists R24571, TFP, W-7, and W-5 inhibit appressorium formation at concentrations which have no effect on germination. The data presented in this paper are consistent with the hypothesis that a Ca2+/calmodulin system is involved in regulating appressorium formation. However, since the direct effects of the drugs were not specifically tested on their proposed binding sites, we leave room for alternative hypotheses that have yet to be formulated.les) requires external Ca2+ for appressorium formation but not for conidial germination. The number of appressoria formed depends on the Ca2+ concentration of the medium. At low [Ca2+] (100 pM) nuclear division and germ tube growth are significantly reduced compared to higher Ca2+ concentrations (10 and 1,000 μM). By contrast, neither external K+ nor external Cl− is needed for germination or appressorium formation. Treatment of conidia with a Ca2+-antagonist, Nd3+, and a Ca2+-channel blocker, nifedipine, inhibits appressorium formation, showing that a Ca2+ influx is required for appressorium formation. Furthermore, the partial yet saturating inhibition by nifedipine and complete inhibition by Nd3+ indicates that at least two kinds of Ca2+ channels are involved in appressorium formation. A contribution of intracellular Ca2+ to the signal transduction chain for the formation of appressoria is demonstrated by the inhibitory effect of the intracellular Ca2+ antagonist TMB-8. The calmodulin antagonists R24571, TFP, W-7, and W-5 inhibit appressorium formation at concentrations which have no effect on germination. The data presented in this paper are consistent with the hypothesis that a Ca2+/calmodulin system is involved in regulating appressorium formation. However, since the direct effects of the drugs were not specifically tested on their proposed binding sites, we leave room for alternative hypotheses that have yet to be formulated

Nuclear Events During Germination and Appressorial Formation of the Entomopathogenic Fungus Zoophthora Radicans (Zygomycetes: Entomophthorales)

Conidial germination, appressorial formation, and secondary sporulation in Zoophthora radicans occurred independently of DNA replication and nuclear division. Video-image analysis combined with epifluorescence microscopy showed that at 18 hr postinoculation, approximately 10% of germlings had undergone the first DNA duplication and nuclear division and that 20% of germlings had formed appressoria. Hydroxyurea, an inhibitor of DNA synthesis, prevented DNA replication and nuclear division but allowed production of germ tubes and appressoria. Actinomycin D, an inhibitor of RNA synthesis, totally inhibited germination at concentrations above 10ug/ml. At lower concentrations, actinomycin D allowed formation of germ ube and appressoria in a dose-dependent fashion. However, even at the lowest concentration tested (1ug/ml), nuclear division and formation of penetration hyphae were prevented. Formation of secondary conidia and capilli-conidia was also independent of nuclear division but was totally inhibited by drugs blocking RNA or protein synthesis. The implications of differentiation without prior nuclear division are discussed

Effect of two dosages of Metarhizium anisopliae var. acridum against Rhammatocerus schistocercoides Rehn Efeito de duas dosagens de Metarhizium anisopliae var. acridum contra Rhammatocerus schistocercoides Rehn

The fungus Metarhizium anisopliae var. acridum, strain CG 423, was tested under field conditions against the gregarious grasshopper Rhammatocerus schistocercoides (Rehn) (Orthoptera: Acrididae). Conidia formulated in a racemic mixture of soybean oil and kerosene were sprayed under field conditions using an ultralow-volume hand-held atomizer Ulva Plus adjusted to deliver 2.9 L/ha. Bands composed of 2nd instar nymphs were treated with either 5.0x10(12) or 1.0x10(13) viable conidia/ha. The number of insects in each band was estimated at day one following spraying and by the end of the field trial (15 to 16 days post-treatment). Reductions in population size reached, in average, 65.8% and 80.4% for bands treated with the higher and lower dosage, respectively. For both dosages, total mortality rates of insects collected at two days post-application, and kept in cages for 14 days under lab conditions, showed no significant differences as compared to that obtained with insects collected immediately after spraying. Healthy insects were fed to native grasses sprayed on the field with 1.0x10(13) viable conidia/ha. Mortality levels of the nymphs fed on grasses collected two and four days post-application were not affected when compared to nymphs fed on grasses collected immediately following application.<br>O fungo Metarhizium anisopliae var. acridum, isolado CG 423, foi avaliado em condições de campo como agente de controle biológico do gafanhoto gregário Rhammatocerus schistocercoides (Rehn) (Orthoptera: Acrididae). Conídios formulados em uma mistura racêmica de óleo de soja e querosene foram pulverizados no campo com a utilização de um atomizador rotativo manual Ulva Plus, calibrado para aplicação de 2,9 L/ha. Bandos com ninfas de 2º estádio foram tratados com o equivalente a 5,0x10(12) ou 1,0x10(13) conídios viáveis/ha. O número de insetos em cada bando foi estimado no 1º dia após a aplicação e ao final do experimento (15 a 16 dias após tratamento). Reduções populacionais médias de 65,8% e 80,4% foram observadas nos bandos tratados com a maior e menor dosagem, respectivamente. Para as dosagens avaliadas, a mortalidade total de insetos coletados aos dois dias após a aplicação e mantidos em gaiolas durante 14 dias, no laboratório, não apresentou diferença significativa daquela obtida para insetos coletados imediatamente após a pulverização. Insetos sadios foram alimentados com gramíneas nativas pulverizadas no campo com 1,0x10(13) conídios viáveis/ha. As taxas de mortalidade observadas nas ninfas alimentadas com capim coletado aos dois e quatro dias após a pulverização não foram afetadas quando comparadas com ninfas alimentadas com capim coletado imediatamente após a pulverização