Assessing the effects of Lecanicillium lecanii in the biological control of early and late leaf spot of peanut in vitro (Burkina Faso, West Africa)

Early and late leaf spots caused by Cercospora arachidicola and Phaeoisariopsis personata respectively, are the most widespread peanut fungal diseases in West Africa. These diseases lead to notable crop losses in the rural area. In the recent decades, chemical fungicides are used to fight against crop losses, but these chemical substances cause big damages to the environment including the animals and human beings. Thus, the biological control is encouraged by scientific community and all government because it is well known to be safety and cost effective. For this reason, we investigated on the effectiveness of Lecanicillium lecanii on leaf spots of peanut in Burkina Faso. To do so, spore suspensions (106 spores / ml) from four strains of L. lecanii was used in vitro. The results revealed that L. lecanii 4181 inhibited the pathogen conidia germination up to 87%, as well as elongation germ tube with highest rate of 56%. Compared to the distilled water control, the severity scores vary between 5.7 and 8, but our results showed a notable decrease of score from 2.3 and 4.7. From our findings, the treatments with L. lecanii spore suspensions on peanut leaves significantly reduced the severity of leaf spots and may be potentially used to promote organic farming in West Africa.