Efficacy of Biological Fungicide Control on Cashew Nuts Lost caused by Colletotrichum gloeosporioïdes Penz. in the North of Côte d’Ivoire

Abstract

Context and Objective: Anthracnose, caused by Colletotrichum gloeosporioïdes, represents the main disease of cashew in the north of Côte d'Ivoire. This study was conducted to assess the toxicity of three synthesis fungicides, Azoxystrobin, Carbendazim and Carbendazim+Chlorothalonil and two essential oils extracted from Cymbopogon nardus and Ocimum gratissimum against Colletotrichum gloeosporioïdes. Material and Methods: Fungicidal properties of these products were evaluated in vitro on mycelial radial growth of C. gloeosporioïdes strain, through six concentrations added to a PDA medium (Potato Dextrose Agar). At the laboratory test, an essential oil, Ocimum gratissimum and the synthetic fungicides based on Azoxystrobine and Carbendazim+Chlorothalonil were selected and tested in situ against anthracnose disease. Résults: After 16 days of incubation at 30 ± 2 °C, the mycelial radial growth of C. gloeosporioïdes was completely inhibited from 1 µL/L by Carbendazim, 5 µL/L of Carbendazim+Chlorothalonil, and 1500 µL/L by essential oil of O. gratissimum. After reeling mycelial disks, the minimum fungicidal concentration obtained was 25 µL/L for Carbendazim, 100 µL/L for Carbendazim+Chlorothalonil and 2000 µL/L for O. gratissimum. The study in situ showed a highly significant reduction of the incidence and the severity of anthracnose on the leaves by essential oil of O. gratissimum. Conclusion : The essential oil of Ocimum gratissimum can be used in biological control of the pathogen Colletotrichum gloeosporioïdes in cashew plantation.