The fall armyworm Spodoptera frugiperda (J.E. Smith), a new pest of maize in Africa: monitoring, damage evaluation and identification of natural enemies on production areas of Senegal

The fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith), an invasive pest of cereal crops in Africa, poses a real threat to food security in sub-Saharan African countries where cereals are the staple food. Since its appearance in Africa in 2016, the FAW has invaded almost all African countries due to its great dispersal capacity. Because of its resistance to a number of chemical pesticides but also the risks associated with the use of these, the search for an alternative method becomes essential. In order to report on the incidence of this pest and explore its associations with native natural enemies, a monitoring study of S. frugiperda populations, its damage as well as its natural enemies was carried out during the period of August to September 2020 in corn fields of two agro-ecological zones of Senegal and in the laboratory. Monitoring results show a heavy infestation with rates of up to nearly 75% of defoliated plants and more than 60% of attacked ears. The damage recorded remains low overall (score below 3/9). A wide range of auxiliary insects (17 families) made up of parasitoids and predators were identified in the field and in the laboratory as well as an endoparasitic nematode with a parasitism rate of 38.46% and a fungus in one of the sites. These results pave the way for the development of an approach to control CLA with these biological agents

Genetic diversity and demographic evolution of baobab (Adansonia digitata L., Bombacoideae, Malvaceae) populations in Senegalese Sahelian areas

This study evaluated the spatial genetic structure of baobab (Adansonia digitata L.) populations from three agroecological sites located in sahelian zone of Senegal using ITS1, 5.8S rDNA and ITS2 gene sequences. To determine the extent of isolation, gene sequences were analyzed between and among three sahelian baobab populations. At least 25 haplotypes of baobab (A. digitata L.) were revealed in Senegal (6, 9 and 10, respectively in Dakar, Bandia and Widou Thiengoly). Private haplotypes found in each locality show that there is an adaptation of the plant to environmental conditions prevailing in each site. Indeed, nucleotide diversity was more important in Dakar (0.00527); it ranges from 0.00483 to 0.00060 for Bandia and Widou populations, respectively. Curves of mismatch distribution show that the population of Ferlo has undergone a recent demographic expansion. Although Bandia and Dakar populations were polyphyletic; each shows a balanced expansion. Fst values ranging from 0.62946 to 0.90712 correlates a strong genetic differentiation between sites. A correlation between geographic and genetic distances was not highlighted by the Mantel’s test but phylogenetic trees of maximum likelihood and Bayesian inference have assigned two clades demonstrating that population of Ferlo (Widou) form a different ecotype from those of Bandia and Dakar.Keywords: ITS1, 5.8S, ITS2, Adansonia digitata, haplotype, genetic diversity, demographic evolutionAfrican Journal of Biotechnology Vol. 12(38), pp. 5627-563

Identification morphométrique des populations de Tribolium castaneum Herbst (Coleoptera, Tenebrionidae) inféodées à trois céréales à Widou Thiengoli

Objectif: Tribolium castaneum, est un coléoptère qui a la capacité d’infester toutes les céréales et légumineuses entreposées. Sa capacité à dérouler son cycle de développement sur divers substrats alimentaires a suscité des réflexions sur son adaptabilité morphologique. Cette étude a pour objectif d’identifier la morphologie de T. castaneum à Widou sur différentes céréales.Méthodologie et résultats: Trois populations ont été définies en fonction de la céréale (maïs, mil ou riz) sur laquelle T. castaneum a déroulé son cycle de développement. Chacune des populations est constituée de 30 adultes mâles. Sur chaque adulte, 19 variables ont été mesurées. Les distances entre des yeux dorsalement et ventralement (Dyd, Dyv), la largeur du fémur_3 (lf3) et des élytres (lme) sont éliminées de l’analyse car ne présentant aucune variabilité entre les différents individus. Les 15 variables restantes sont utilisées pour des Analyses en Composante Principale. La taille est le premier facteur qui discrimine la population mil des autres. Suite à la transformation logarithmique des données brutes, l’Analyse discriminante a montré une différence de forme entre les trois populations. La classification ascendante hiérarchique a montré trois groupes morphométriques. Le groupe_1 dominé par les individus du mil est plus morphologiquement homogène. Le groupe_2 est dominé par les individus du riz et le groupe_3, le plus morphologiquement hétérogène, ne renferme que des individus du maïs.Conclusion et application des résultats: Ce présent travail contribue à la mise en place d’une lutte intégrée contre T. castaneum. La connaissance de la diversité populationnelle de ce ravageur primaire des céréales stockées est nécessaire pour la mise en place une lutte adaptée selon sa variabilité morphogénétique.Mots clés: Tribolium castaneum, biotype, ACP, morphométrie, AD, Widou Thiengoli, CAHEnglish Title: Morphometric identification of populations of Tribolium castaneum Herbst (Coleoptera, Tenebrionidae) subservient to three cereals at Widou ThiengoliEnglish AbstractObjective: Tribolium castaneum is a beetle that has the ability to infest all stored cereals and legumes. Its ability to unfold its development cycle on various food substrates has prompted reflections on its morphological adaptability. This study aims to identify the morphology of T. castaneum in Widou Thiengoli on different cereals.Methodology and results: Three populations were defined according to cereals (maize, millet or rice) on which T. castaneum developed its development cycle. Each population consists of 30 adult males. On each adult, 19 variables were measured. The distances between the dorsal and ventral eyes (Dyd, Dyv), the width of the femur_3 (lf3) and the elytra (lme) are eliminated from the analysis because no variability between the different individuals. The remaining 15 variables are used for Principal Component Analyzes. Size is the primary factor that discriminates the millet population of others. Following the logarithmic transformation of the raw data, Discriminant Analysis showed a difference in shape between the three populations. Hierarchical ascending classification showed three morphometric groups. The group_1 dominated by biotype millet individuals is more morphologically homogeneous. Rice individuals dominate group 2 and group 3, the most morphologically heterogeneous, contains only maize individuals.Conclusion and application of results: There is a morphological difference between the three populations of T. castaneum defined according to the food support, but the hypothesis of a morphological adaptation of T. castaneum on different food substrates can only be confirmed by varying the geographical sites. This present work contributes to the setting up of integrated struggle of T. castaneum. Knowledge of the population diversity of this primary pest of stored grains is necessary for the setting up of an adapted struggle according to its genetic variability.Keywords: Tribolium castaneum, biotype, PCA, morphometry, AD, Widou Thiengoli, CA

Dynamique des Troupeaux de Petits Ruminants Saheliens dans Les Exploitations Rurales au Senegal

Les races locales de petits ruminants (PR) sahéliens du Sénégal sont très adaptées à l’élevage extensif malgré les contraintes alimentaires et sanitaires surtout dans le contexte actuel de changement climatique. Importante source de protéines pour les populations, les PR leur génèrent aussi des revenus substantiels. En dépit de cette importance socio- économique, peu d’études ont porté sur les performances et la gestion des animaux dans leur environnement d’élevage. L’objectif de ce travail est d’étudier la dynamique des troupeaux de PR dans la zone semi-aride du Ferlo. Ainsi, des enquêtes rétrospectives transversales par la méthode des 12 derniers mois ont étéréalisées dans 52 troupeaux ruraux durant le mois d‘avril 2017. Sur l’ensemble des troupeaux enquêtés 604 ovins et 450 caprins ont été enregistrés avec des tailles moyennes de 19,48±9,63 et 21,43±11,35 têtes par troupeau respectivement pour les ovins et les caprins. Le taux de mises-bas annuel est de 84,1 ± 5,4% pour les chèvres et 85,5 ± 5,3% pour les brebis. La mortalité a particulièrement touché les jeunes animaux avec des fréquences respectives de 16,8 ± 3,0 et 13,2 ± 3,0% pour les ovins et les caprins. L’achat a été le principal motif d’entrée d’animaux dans les exploitations tandis que la mortalité et la vente ont constitué les principaux motifs de sortie respectivement pour les ovins et les caprins. Le taux d’exploitation de 23,8 ± 2,1% pour les ovins contre 26,8 ± 2,5% pour les caprins et les mâles adultes sont principalement les plus exploités. Les contraintes et constats identifiés dans cette étude doivent être pris en compte pour le développement des filières ovine et caprine dans la zone semi-aride du Sénégal. Local breeds of Sahelian small-ruminant (SR) in Senegal are highly adapted to extensive farming systems despite feeding and health constraints, especially in a climate change context. As an important source of protein for populations, SR also generate substantial income. Despite this importance, their productivity in rural farming systems is rarely studied. The main objective of this study is to analyze demographic dynamics of SR’s flocks in the Ferlo zone using last twelve months retrospective surveys. The surveys were carried out on 52 flocks belonging to 32 rural households. With a predominance of adult females, a total number of 604 sheep and 450 goats are counted with an average size of 19.48 ± 9.63 and 21.43 ± 11.35 heads per flockrespectively for sheep and goat. The annual birth rate was 84.1 ± 5.4 for goats and 85.5 ± 5.3% for sheep. Young animals were particularly affected by mortalitywith a frequency of 16.8 ± 3.0 and 13.2 ± 3.0% respectively for sheep and goats. Purchase was the main reason for entrance of animals into the flocks. For animal exits, mortalities were the main reason for sheep whereas for goats, sales were the main reasons. The global offtake rate was 23.8 ± 2.1% for sheep and 26.8 ± 2.5% for goats and adult males were mostly concerned. Despite low productivity, SR breeding remains an important economic activity for the rural populations

Genetic diversity of bovine populations raised in Senegal

BACKGROUND: The Gobra zebu and N'dama taurine cattle breeds are important genetic animal resources for Senegal. For several decades, genetic breeding programmes have been devoted to them at the Centre de Recherches Zootechniques de Dahra and Kolda. Since then, these animals have been subjected to mass selection, mainly in closed selection nuclei. OBJECTIVE: This study aims to assess the genetic diversity within these selection nuclei in order to orient future selection strategies. MATERIAL AND METHODS: The study was carried out on the Gobra zebu and N'dama taurine populations from selection nuclei of Dahra and Kolda respectively, which were compared to 5 other populations of the main cattle breeds in Senegal. One hundred eighty (180) animals were genotyped with 21 microsatellite markers recommended by the Food and Agriculture Organisation. RESULTS: All populations were found to be polymorphic with a PIC of over 55%. However, animals from the CRZ‐Dahra (indigenous) and CRZ‐Kolda stations had the lowest mean heterozygosity (0.643 and 0.591 respectively). The other populations had an average heterozygosity between 0.650 and 0.737. CONCLUSION: The cattle populations maintained at the different CRZs show a lower genetic diversity than the other populations described in our study. The main reasons for this are reproductive isolation and selection pressure on these populations

Incidence et régulation naturelle de la chenille mineuse de l'épi du mil, Heliocheilus albipunctella de Joannis (Lepidoptera, Noctuidae) à Bambey dans le bassin arachidier au Sénégal

Au Sénégal,la mineuse de l'épi,Heliocheilus albipunctella (Lepidoptera, Noctuidae)a commencé à causer des dégâts dans les cultures de mil suite à une longue période de sécheresse au début des années 70. Le suivi d'un réseau de 45 parcelles de producteurs à Bambey en 2013, a permis d'évaluer la situation du ravageur : abondance relative (oeuf et larve, parasitisme associé, potentiel de régulation naturelle et pertes de rendement liées aux dégâts. Les résultats ont montré une distribution très hétérogène du ravageur dans la zone avec des moyennes d'infestation des épis en oeufs de 40 % et en larves 76 %. Un taux moyen de parasitisme des oeufs par Trichogrammatoïdea sp estimé à 2 % est noté (n = 2281 oeufs). Le parasitisme larvaire est dominé par des cocons d'endoparasitoïdes de la famille des Ichneumonidae (8,6 %), des larves de Tachinidae (5,2 %) et des morphotypes non encore identifiés (4,6 %. Une faible mortalité larvaire due au Bracon sp. (1,5 %, n = 1567 larves) est observée. Ce faible taux de parasitisme, comparé au potentiel réel de la régulation naturelle observée (59 %, n = 45 parcelles) montre l'importance probable des ennemis naturels dans le contrôle du ravageur. Les pertes en grains sont estimées à 10 %. (Résumé d'auteur

Genetic differentiation of groundnut seed-beetle populations in Senegal

#Caryedon serratus, the groundnut seed-beetle, is a major pest of groundnut (#Arachis hypogaea), an introduced legume in the subfamily #Papilionoideae. Native hosts of #C. serratus in Senegal include #Bauhinia rufescens, #Cassia sieberiana, #Piliostigma reticulatum and #Tamarindus indica, all of which belong to the legume subfamily #Caesalpinioideae. The biology and natural history of #C. serratus suggest that it is a candidate for population differentiation via host-race formation. Evidence for host-tree associated differentiation in #C. serratus would be important for the design of rational pest management practices. To test this possibility, we analyzed the genetic structure of 20 adult collections of #C. serratus from six sites in Western Senegal, on its five hosts. Results show a strong differentiation of insects from different host trees, with specimens from #C. sieberiana possibly representing a sibling species and insects from #B. rufescens a distinct host-race. (Résumé d'auteur

Genetic differentiation of groundnut seed-beetle populations in Senegal

#Caryedon serratus, the groundnut seed-beetle, is a major pest of groundnut (#Arachis hypogaea), an introduced legume in the subfamily #Papilionoideae. Native hosts of #C. serratus in Senegal include #Bauhinia rufescens, #Cassia sieberiana, #Piliostigma reticulatum and #Tamarindus indica, all of which belong to the legume subfamily #Caesalpinioideae. The biology and natural history of #C. serratus suggest that it is a candidate for population differentiation via host-race formation. Evidence for host-tree associated differentiation in #C. serratus would be important for the design of rational pest management practices. To test this possibility, we analyzed the genetic structure of 20 adult collections of #C. serratus from six sites in Western Senegal, on its five hosts. Results show a strong differentiation of insects from different host trees, with specimens from #C. sieberiana possibly representing a sibling species and insects from #B. rufescens a distinct host-race. (Résumé d'auteur