Evaluation naturelle de l’impact de Beauveria bassiana : Champignon enthomopathogène dans la dynamique de population de Hypothenemus hampei, scolyte de baies des cerises de Coffea canefora

A study of finding out natural enemies of the coffee cherry borer beetle Coffea canephora, Hypothenemus hampei (Ferrari) (Coleoptera, Scolytidae) was carried out at two ecologically different sites of Cameroon: Nkoemvone in the South region of the country and Nkolbisson around Yaoundé in the central region. For six months, 500 berries were randomly collected monthly at each site. The presence of entomopathogenic fungus was observed on berries infested by the borer beetle. Rates of borer insect mortality due to Bauveria bassiana at Nkoemvone are: 70.6% in August, 64.6% in September, 32% in October, 43.2% in November, 39.2% in December and very low in January (8.6%). On the other hand, these rates at Nkolbisson are: 42.6% in October, 10% in November, 3.4% in December, 2.6% in January, 1.4% in February and 0% in March. From these observations, it was possible to carry out a research on the pathogenicity tests through its natural presence and on artificial-infection trials of the borer beetle with this fungus in order to protect better the coffee grains with a biological product

Qualité du cacao camerounais : Facteurs influençant la présence et l’activité des moisissures productrices de l’ochratoxine A (OTA)

La qualité du cacao peut être influencée par la microflore fongique, en particulier toxinogène. Des cabosses de cacao, récoltées dans la région de Kumba au Cameroun, ont subi deux types de traitements post-récolte (fermentation en caisse et en tas de cabosses saines ou blessées). La numération des moisissures contaminantes donne une teneur maximalede 5,5 ± 1,4 x 107 CFU.g-1. Quel que soit l’état des cabosses traitées et le type de traitement, la microflore fongique totale reste qualitativement identique. Elle est essentiellement constituée d’Aspergillus niger aggregate, A. carbonarius, A. flavus, A. tamari, A. fumigatus, Penicillium sclerotiorum, P. crustosum, P. paneum, Fusarium spp. L’étude de la toxinogénèse montre que, parmi les souches isolées, seuls Aspergillus carbonarius et A. niger sont capables de produire l’OTA avec desteneurs maximales égales à 2.772 ng/g et 3,6 ng/g respectivement. Le cacao issu des cabosses abîmées est le plus contaminé par les moisissures toxinogènes et donc par l’OTA. L’étude des conditions de toxinogénèse de A. carbonarius montre une forte sensibilité à l’activité de l’eau du milieu.. Cocoa quality can be influenced by the fungal microflora, in particular the toxinogenic one. Cocoa pods, harvested in Kumba region of Cameroon, were submitted to two types of post - harvest treatments (fermentation in boxes and in heap of healthy either wounded cocoa pods). The numeration of contaminating moulds gives a maximal content of5.5 ± 1.4 x 107 UCF.g-1. Whatever the state of treated pods is and the type of treatment, the total fungal microflora remained qualitatively identical. It is essentially constituted of Aspergillus niger aggregate, A. carbonarius, A. flavus, A. tamari, A. fumigatus, Penicillium sclerotiorum, P. crustosum, P. paneum, Fusarium spp,. The study of the toxinogenesisshows that, among isolated strains, only Aspergillus carbonariuses and A. niger are able to produce Ochratoxin A with respective maximal contents of 2.772 ng/g and 3,6 ng/g. The cocoa from damaged pods is more contaminated by toxinogenic moulds and therefore by Ochratoxin A. The study of toxinogenic conditions of A. carbonarius shows a strong sensitivity to the water activity of the media.