Evaluation de l’efficacité d’un bio-fongicide à base de Lecanicillium lecanii (Zimmerm) sur les cercosporioses de l’arachide (Arachis hypogaea L.) en milieu réel

La lutte biologique est une méthode alternative à la lutte chimique ayant des effets néfastes sur la santé des producteurs, des consommateurs et de l’environnement. Les maladies foliaires, en l’occurrence les cercosporioses causées par Cercospora arachidicola et Phaeoisariopsis personata handicapent la production arachidière dans le monde en général, et particulièrement au Burkina Faso. Cette étude a consisté à utiliser une souche A de Lecanicillium lecanii, à des traitements différents contre le développement des cercosporioses. Pour ce faire, quatre traitements, T1, T2, T3 et T4, ont été appliqués sur deux variétés, la TS32-1 et la PC79-79 respectivement chaque deux jour, chaque semaine, chaque dix jour et chaque deux semaine. Le dispositif expérimental est un bloc de Fisher complètement randomisé à trois répétitions, constituée chacune de 5 blocs dont 4 blocs correspondant chacun à un traitement et un bloc constituant le témoin. L’étude, conduite à Gampèla, au Burkina Faso a permis de mesurer les paramètres tels que la levée au 21ème JAS, la densité de peuplement au 32ème JAS, l’incidence des cercosporioses et l’envahissement foliaire, le taux de survie, le pourcentage de défoliation et les composantes de rendement. L’étude a permis de montrer que les traitements ont eu un effet réductif sur le développement des cercosporioses au niveau des deux variétés, surtout sur la variété sensible TS32-1. Le traitement effectué chaque deux jour a donné le meilleur contrôle des cercosporioses avec une note moyenne de 3,5 sur TS32- 1 et de 2,75 sur PC79-79. Sur les composantes du rendement, les traitements ont également permis d’obtenir de bons résultats comparés aux résultats du témoin pour les deux variétés. En effet, le témoin a enregistré de 318,7 et 402,3 kg/ha respectivement pour les variétés TS32-1 et PC79-79 et les autres traitements ont obtenu des rendements compris entre 507,7 et 1656,7 kg/ha. Biological control is an alternative method to chemical control, which has adverse effects on the health of producers, consumers and the environment. Foliar diseases, in this case cercosporioses caused by Cercospora arachidicola and Phaeoisariopsis personata, handicap peanut production in the world in general, and particularly in Burkina Faso. This study consisted in using a Lecanicillium lecanii strain A, with different treatments against the development of cercosporioses. To do this, four treatments, T1, T2, T3 and T4, were applied to two varieties, TS32-1 and PC79-79 respectively every two days, every week, every ten days and every two weeks. The experimental set-up was a completely randomised Fisher block with three replicates, each consisting of five blocks, four of which corresponded to a treatment and one to a control. The study, conducted in Gampèla, Burkina Faso, measured parameters such as emergence at 21 days after planting, stand density at 32 days after planting, incidence of cercosporiosis and leaf invasion, survival rate, defoliation percentage and yield components. The study showed that the treatments had a reducing effect on cercosporium development in both varieties, especially in the susceptible variety TS32-1. The treatment applied every second day gave the best cercospora control with an average score of 3.5 on TS32-1 and 2.75 on PC79- 79. On the output components, the treatments also performed well compared to the control for both varieties. Indeed, the control recorded 318.7 and 402.3 kg/ha for TS32-1 and PC79-79 respectively and the other treatments obtained yields between 507.7 and 1656.7 kg/ha

Parasitic fungi of sweet grain sorghum in Burkina Faso: risks of its consumption in the absence of hygienic rules

 Sweet grain sorghum [Sorghum bicolor (L.) Moench] is a staple food in rural Africa and is mainly grown for its grains, which are consumed in a paste-like state. It is nowadays attacked by numerous parasitic fungi, hence this study was carried out with the objective to characterize the fungal pathogens associated with this crop from the seed, vegetative stage, to the doughy grain stage at harvest. For this purpose, 37 genotypes of seeds of this crop, obtained from the Genebank of the Plant Genetics and Breeding team, Biosciences Laboratory of the Joseph KI-ZERBO University of Burkina Faso, were subjected to sanitary analysis. All the genotypes were tested during the 2021 rainy season using an alpha lattice design with three replications. From the 30th day of the rainy season, symptomatic leaves were randomly collected from 11 genotypes of each replicate for the isolation and characterization of different fungal pathogens. Similarly, from day 90 onwards, the health status of the doughy grains was analyzed on the same genotypes. The results obtained revealed a diversity of fungal pathogens both on seeds in pre-sowing, on symptomatic leaves and on doughy grains in pre-harvest. Indeed, 10 fungal species were found on the selected genotypes, among which seven species of fungi were identified as pathogens of sweet grain sorghum, namely Bipolaris sp., Curvularia lunata, Fusarium moniliforme, Phoma sorghina, Colletotrichum graminicola, Nigrospora oryzae and Exserohilum sp. In addition, three saprotrophic fungi namely Aspergillus flavus, Aspergillus niger and Rhizopus sp., which account for 30% of the pre-sown seed and pre-harvest doughy grain, were also identified. Curvularia lunata (61.61%), Fusarium moniliforme (53.53%) and Phoma sorghina (42.42%) were the most abundant and common fungal pathogens at the development stages studied. To sum up, the existence of a number of parasites and saprotrophs fungi on grains of this crop, generally consumed in their fresh state, is a significant threat to humans because they could secrete mycotoxins, mainly fusariotoxins, which could lead to the occurrence of certain mycoses in humans in the long term. Hence there is a need to apply basic hygiene rules for a healthy consumption of these grains. &nbsp