Memoirs of the Entonological Society of Canada l7l: 265-286 (1991) Four research programmes are investigating the entomopathogenic fungal genera Metat hiziunt and Beauveria for locust and grasshopper control in Africa. ln the LUBILOSA programme, surveys for pathogen isolates revealed a morphologically distinctive Metarhizium t'lavoviride Gams and Rozsypal attacking acridoids in West Africa, Madagascar, and elsewhere. Metarhizium anisopliae (Metschnikoff) Sorokin isolates with virulence to acridoids were also obtained, including several from non-orthopteran hosts. Natural epizootics ofboth genera are rare in acridoid populations, but do occur. A standardized screening method discriminated virulent from non-vitulent isolates. The great majority of the most virulent isolates were from the acridoid group of M . JIat,oviride. A Niger isolate chosen for development from this group had 1ow virulence to honey bees and parasitic Hymenoptera and was not infective to insects in several otler orders. Field tests were carried out on fo^rmulations of oil mixtures, using ULV application rates of l-2Llha and2-5 x l0'' conidia per hectare. In preliminary tests, target insects were sprayed successfully in small field arenas and in large cages. Trials

Following the droughts that occurred in the Sahel during the 1970s, the Senegalese grasshopper Oedaleus senegalensis (Krauss 1877) suddenly became the main pest grasshopper species in this region, where it regularly causes serious damage to crops, especially millet. The lifecycle of O. senegalensis refl ects the precariousness of the Sahelian environment. The lifecycle and survival strategies of O. senegalensis have evolved to include migration following shifts in the intertropical convergence zone (ITCZ) and embryonic diapause in the dry season. It is thus able to cope with its natural hostile environment and remain in the most suitable ecological conditions for as long as possible. The alternation between outbreaks and recession periods seems to be related to the high spatiotemporal rainfall variability in the Sahel. Senegalese grasshopper outbreaks depend on the rainy season chronological pattern and on the initial quantity of diapaused eggs in the soil. Since the 1970s, many studies have been conducted on this species in the Sahel. Various models designed to monitor the population dynamics of this species have been published. However, some key factors that could explain the variability in outbreaks have not been seriously investigated. The present bibliographical review provides an overview on current knowledge while proposing some avenues for future research to enhance the sustainable management of this major Sahelian pest. Résumé. Ecologie et contrôle du criquet sénégalais Oedalus senegalensis (Krauss 1877) (Orthoptera : Acrididae) en Afrique Occidentale : revue et perspectives. Depuis les années 1970, le criquet sénégalais-Oedaleus senegalensis (Krauss 1877)-est devenu l'un des principaux criquets ravageurs des cultures vivrières du Sahel africain. Il cause régulièrement des dégâts considérables, en particulier sur le mil. Le cycle biologique de ce criquet refl ète la précarité de l'environnement sahélien. Cette espèce a développé un cycle biologique et une stratégie de survie incluant à la fois des migrations saisonnières suivant le déplacement du Front Intertropical (FIT) et une diapause embryonnaire pendant la saison sèche. Cela lui permet de faire face à un environnement souvent hostile et, pendant la saison des pluies, de se maintenir dans les conditions écologiques les plus favorables possibles. La succession de périodes de pullulations et d'accalmie est liée à la forte variabilité spatiale et temporelle de la pluviométrie et à l'abondance du stock d'oeufs en diapause dans le sol en fi n de saison sèche. Les nombreux travaux conduits au Sahel depuis les années 1970 ont permis une meilleure compréhension de l'écologie de cette espèce. Divers modèles ont été proposés pour suivre la dynamique de ses populations. Cependant, certains facteurs clés pouvant permettre d'expliquer les pullulations demeurent peu ou pas étudiés. La présente revue bibliographique fait le point sur les connaissances actuelles et propose des voies de recherche pour une gestion durable de ce ravageur.

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