Facteurs affectant les épizooties de entomophaga grylli (zygomycètes, entomophthorales) chez les populations du criquet zonocerus variegatus au sud du bénin en afrique de l’ouest

L’étude en champ des facteurs affectant les épizooties de Entomophaga grylli chez les populations de Zonocerus variegatus, dans les quatre départements au Sud du Bénin, a montré que E. grylli est l’un des principaux facteurs de mortalité des larves âgées du criquet. Les infections ont lieu principalement de novembre à février, pendant la période de saison sèche où les densités de populations de Z. variegatus sont élevées dans l’ensemble de la zone, contrairement à celles de la saison pluvieuse. Les densités observées à cette période pluvieuse sont négligeables. Les épizooties ont été importantes au cours des saisons 1995-1996 et 1996-1997. Pendant la saison 1996-1997, la prévalence de l’infection a atteint au maximum 10%, 14%, 24% et 46% respectivement à Agbata, Lama 1, Lama 3 et Lama 2. Entre novembre 1996 et début janvier 1997, le taux moyen d’infection a varié entre 4 et 10%, notamment à Agbata et Lama 3, mais était supérieur à 15% à Lama 2. En 1997-98, les épizooties étaient très faibles, variant entre 0 et 2% sur la plupart des sites, sauf à Hinvi où elles ont atteint 14%. Parmi les facteurs abiotiques examinés,à savoir la température, la pluviométrie, l’humidité relative et la radiation solaire, cette dernière est apparue comme le principal facteur ayant régulé les épizooties au cours des trois saisons.Mots clés: Zonocerus variegatus, Entomophaga grylli, Entomophthorales, épizootie.The seasonal occurrence of Entomophaga grylli on Zonocerus variegatus populations was monitored in the four Southern departments of Benin. The study showed that E. grylli was one of the major mortality factors of grasshopper’s larvae. Infections occurred principally from november to february during dry season when Z. variegatus populations are important. Densities observed at this period are generally high in the studied zones,contrary to those of wet season witch are negligible. Epizootics were important during 1995-96 and 1996-97 seasons. During 1996-97, prevalence of infection reached in maximum 10%, 14%, 24% and 46% the 11 December at Agbata, Lama 1, Lama 3 and Lama 2 sites respectively. Between November 1996 and start January, infection mean rate varied from 4 to 10 % notably at Agbata and Lama 3, but was more than 15% at Lama 2. In 1997-98 epizootics were very few, between 0 and 2 % on the majority sites, but not at Hinvi were a maximum of 14% was reached in 1997. Among abiotic factors examined, namely temperature, relative humidity and solar radiation, this last appeared to be the principal epizootics regulating factor

Phosphine Resistance in the Rust Red Flour Beetle, Tribolium castaneum (Coleoptera: Tenebrionidae): Inheritance, Gene Interactions and Fitness Costs

The recent emergence of heritable high level resistance to phosphine in stored grain pests is a serious concern among major grain growing countries around the world. Here we describe the genetics of phosphine resistance in the rust red flour beetle Tribolium castaneum (Herbst), a pest of stored grain as well as a genetic model organism. We investigated three field collected strains of T. castaneum viz., susceptible (QTC4), weakly resistant (QTC1012) and strongly resistant (QTC931) to phosphine. The dose-mortality responses of their test- and inter-cross progeny revealed that most resistance was conferred by a single major resistance gene in the weakly (3.2×) resistant strain. This gene was also found in the strongly resistant (431×) strain, together with a second major resistance gene and additional minor factors. The second major gene by itself confers only 12–20× resistance, suggesting that a strong synergistic epistatic interaction between the genes is responsible for the high level of resistance (431×) observed in the strongly resistant strain. Phosphine resistance is not sex linked and is inherited as an incompletely recessive, autosomal trait. The analysis of the phenotypic fitness response of a population derived from a single pair inter-strain cross between the susceptible and strongly resistant strains indicated the changes in the level of response in the strong resistance phenotype; however this effect was not consistent and apparently masked by the genetic background of the weakly resistant strain. The results from this work will inform phosphine resistance management strategies and provide a basis for the identification of the resistance genes

Influences des vapeurs d'huiles esentielles extraites de trois plantes aromatiques de C&#244te d'Ivoire sur Callosobruchus maculatus

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