Evaluating the efficacy of Moringa oleifera leaf extract in controlling Cercospora leaf spot disease in groundnut (Arachis hypogaea)

Cercospora leaf spot (CLS) is a major leaf disease affecting groundnut production in Nigeria and other tropical countries. This study aimed to evaluate the efficacy of Moringa oleifera leaf extracts (MLEs) in controlling CLS, enhancing plant growth, and improving yield under both in vitro and field conditions. In the in vitro experiments, different concentrations (0, 2, 4, 6, 8, and 10 g ml−1) of MLEs were assessed for their effects on the mycelial growth of Cercospora arachidicola. In field experiments, treatments with MLEs (1.5 and 3.5 kg ha−1), benomyl, and a control were evaluated for their impact on the incidence and severity of CLS, as well as on plant growth and yield. The results showed that MLEs at various concentrations significantly (p < 0.05) reduced the incidence and severity of CLS on groundnut plants. MLEs substantially decreased leaf spot lesion size (by 8.05% to 27.82%) compared to untreated plants (52.04%). There was a significant increase in vegetative growth and yield components compared to the control. Groundnut yield increased by more than 50% following treatment with MLE. Generally, the application of MLE was as effective as the benomyl treatment. Among the treatments, MLE at 3.5 kg ha−1 yielded the best results compared to the control and the other treatments. Therefore, it is recommended to apply MLEs at 3.5 kg ha−1 as a foliar treatment to achieve a lower incidence of CLS and higher vegetative growth and yield in groundnut. Additionally, two foliar sprays of MLE at two week intervals could potentially serve as an effective control measure against CLS in groundnut.