Les ennemis naturels d'insectes du cotonnier au Tchad : premières données sur les champignons de l'ordre des Entomophthorales

En 1986 et en 1987, des épizooties à entomophthorales (zygomicètes) ont été observées dans des populations du puceron #Aphis gossypii et dans des populations adultes de l'aleurode #Bemisia tabaci évoluant sur cotonnier dans le sud du Tchad. C'est la première fois que la présence d'entomophthorales est signalée dans ce pays. Les auteurs présentent tout d'abord le cycle biologique de ces champignons entomopathogènes et les différents éléments morphologiques qui y sont impliqués. Etant donné qu'il est indispensable de récolter et de préparer correctement les insectes tués par une entomophthorale afin de pouvoir identifier celle-ci, les techniques utilisées sont ensuite détaillées. Les symptômes de la mycose d'#Aphis gossypii sont alors décrits et la morphologie respective des spores de résistance, des conidies primaires et des capilloconidies de l'agent responsable, #Neozygites fresenii, est illustrée. L'entomophthorose des adultes de #Bemisia tabaci est due à une espèce inédite de zoophthora, dont la description sera présentée par ailleurs. Les auteurs précisent, cependant, les symptômes de la mycose et illustrent à l'aide d'une autre espèce la morphologie caractéristique des conidies primaires et des capilloconidies au sein du genre Zoophthora. Jusqu'aux observations effectuées au Tchad en 1986 et en 1987, aucun cas d'entomophthorose n'était connu sur #Bemisia tabaci. (Résumé d'auteur

Les ennemis naturels d'insectes du cotonnier au Tchad : premières données sur les champignons de l'ordre des entomophthorales

En 1986 et en 1987, des épizooties à Entomophthorales (Zygomycètes) ont été observées dans des populations du puceron Aphis gossypii et dans des populations adultes de l'aleurode Bemisia tabaci évoluant sur cotonnier dans le sud du Tchad. C'est la première fois que la présence d'Entomophthorales est signalée dans ce pays. Les auteurs présentent tout d'abord le cycle biologique de ces champignons entomopathogènes et les différents éléments morphologiques qui y sont impliqués. Etant donné qu'il est indispensable de récolter et de préparer correctement les insectes tués par une Entomophthorale afin de pouvoir identifier celle-ci, les techniques utilisées sont ensuite détaillées. Les symptômes de la mycose d'Aphis gossypii sont alors décrits et la morphologie respective des spores de résistance, des conidies primaires et des capilloconidies de l'agent responsable, Neozygites fresenii, est illustrée. L'entomophthorose des adultes de Bemisia tabaci est due à une espèce inédite de Zoophthora, dont la description sera présentée par ailleurs. Les auteurs précisent, cependant, les symptômes de la mycose et illustrent à l'aide d'une autre espèce la morphologie caractéristique des conidies primaires et des capilloconidies au sein du genre Zoophthora. Jusqu'aux observations effectuées au Tchad en 1986 et en 1987, aucun cas d'entomophthorose n'était connu sur Bemisia tabac

Biological control of cereal Aphids with Entomophthorales

Research done in France on Entomophthorales attacking cereal aphids gave published results in very numerous fields: biology, ecology, syste- matics, biochemical characterization of strains, physiology of growth and sporulation, production and formulation of inoculum, measure of infectivity, determination of factors governing the pathogenicity. Under oceanic climate, in western France, Erynia neoaphidis is the most effective and constant natural enemy of cereal aphids. In continental France the effect of Entomophthorales is more irregular but E. neoaphidis and Entomophthora planchoniana can develop spectacular epizootics. In green houses it is possible to permanently establish the disease after spraying an industrially produced inoculum. However the enzootic development of the entomophthorosis is not able to prevent the increase of the aphid populations. Major difficulties are: selection of the best suitable strain for the control strategy, depending on the population level, and obtaining an inoculum physiologically closer to that natural one. When taking into consideration the leading part often played by Entomophthorales in the regulation of aphid populations, further research is needed in these priority areas. (Résumé d'auteur

Occurrence of entomopathogenic fungi in soils in Southern Italy

The natural occurrence of entomopathogenic fungi was investigated in Southern Italian soils using larvae of Galleria mellonella L. (Lepidoptera: Galleriidae) as “bait insect”. Since September (1996) to March (1997) 188 samples of soil were collected from different habitats (woodland, orchard, field, seacoast, grassland, uncultivated land and salt pan). Parasitic fungi were obtained from 14.9% of the soil samples. There were 3 entomopathogenic species: Metarhizium anisopliae (Metchnikoff) Sorokin, Paecilomyces lilacinus (Thom) Samson and Beauveria bassiana (Balsamo) Vuillemin. The most common fungal pathogen was B. bassiana. Both M. anisopliae and P. lilaci- nus were isolated only once. The occurrence of B. bassiana seems to be affected by the soil type and the habitat. Key words: survey, Beauveria bassiana, Metarhizium anisopliae, Paecilomyces lilacinus. FUNGHI ENTOMOPATOGENI NEI TERRENI DELL’ITALIA MERIDIONALE È stata effettuata un’indagine per valutare la presenza e la distribuzione di funghi entomopatogeni nei terreni dell’Italia meridionale utilizzando larve di Galleria mellonella L. (Lepidoptera: Galleriidae) come insetto esca. Da settembre 1996 a marzo 1997, sono stati esaminati 188 cam- pioni di terreno provenienti da diversi biotopi. Sono state rinvenute larve infettate da funghi in 28 campioni (14,9%) e sono state identificate 10 specie di funghi parassiti di cui 3 propriamente entomopatogeni: Metarhizium anisopliae (Metchnikoff) Sorokin, Paecilomyces lilacinus (Thom) Samson e Beauveria bassiana (Balsamo) Vuillemin. Il fungo patogeno rinvenuto con maggior frequenza è risultato essere B. bassiana. La sua presenza sembra correlata alle caratteristiche del suolo e dell’habitat. Parole chiave: indagine, Beauveria bassiana, Metarhizium anisopliae, Paecilomyces lilacinus

In Vitro Evaluation of a Soluble Leishmania Promastigote Surface Antigen as a Potential Vaccine Candidate against Human Leishmaniasis

International audiencePSA (Promastigote Surface Antigen) belongs to a family of membrane-bound and secreted proteins present in severalLeishmania (L.) species. PSA is recognized by human Th1 cells and provides a high degree of protection in vaccinated mice.We evaluated humoral and cellular immune responses induced by a L. amazonensis PSA protein (LaPSA-38S) produced in aL. tarentolae expression system. This was done in individuals cured of cutaneous leishmaniasis due to L. major (CCLm) or L.braziliensis (CCLb) or visceral leishmaniasis due to L. donovani (CVLd) and in healthy individuals. Healthy individuals weresubdivided into immune (HHR-Lm and HHR-Li: Healthy High Responders living in an endemic area for L. major or L. infantuminfection) or non immune/naive individuals (HLR: Healthy Low Responders), depending on whether they produce high orlow levels of IFN-c in response to Leishmania soluble antigen. Low levels of total IgG antibodies to LaPSA-38S were detectedin sera from the studied groups. Interestingly, LaPSA-38S induced specific and significant levels of IFN-c, granzyme B and IL-10 in CCLm, HHR-Lm and HHR-Li groups, with HHR-Li group producing TNF-a in more. No significant cytokine response wasobserved in individuals immune to L. braziliensis or L. donovani infection. Phenotypic analysis showed a significant increasein CD4+ T cells producing IFN-c after LaPSA-38S stimulation, in CCLm. A high positive correlation was observed between thepercentage of IFN-c-producing CD4+ T cells and the released IFN-c. We showed that the LaPSA-38S protein was able toinduce a mixed Th1 and Th2/Treg cytokine response in individuals with immunity to L. major or L. infantum infectionindicating that it may be exploited as a vaccine candidate. We also showed, to our knowledge for the first time, the capacityof Leishmania PSA protein to induce granzyme B production in humans with immunity to L. major and L. infantum infectio

Fungi as biological control agents of arthropods of agricultural and medical importance

SUMMARYThere are many species of fungi attacking terrestrial and aquatic insects of agricultural and medical importance. Of these, few species have received much attention with a view to their use as biological control agents. The mechanisms of infection have been comparatively well studied, although many questions remain to be answered. The knowledge so far obtained has shed some light on the reasons for host specificity. Temperature, above all relative humidity, and their interactions are the most important physical factors influencing infection of terrestrial insects by entomopathogenic fungi and these are discussed in relation to epizootiological events. In aquatic environments, temperature, salinity and organic pollution are the important factors. In addition to these physical factors, numerous biotic factors at the level of the insect and the fungal pathogen influence both infection and spread of disease in insect populations. The complexity of the interactions of the biotic and abiotic factors makes it extremely difficult to study the influence of any one of these. Virulence of fungal pathogens and its measurement are discussed, together with the shortcomings of present bioassay systems; virtually no laboratory bioassay system exists which has been designed to yield data meaningful in the field. Mass-production techniques are described as are their inherent problems and those of formulation and storage. Finally, the achievements of fungal control of insects in the field are reviewed. Thus far, several species are mass-produced and are in widespread use, two of which,Verticillium lecaniiandHirsutella thompsonii, have been commercialized. More studies, ecological, fundamental and developmental are required in this field to realize fully the potential of other candidate fungi.</jats:p