Efficacy of plants extracts on cercospora leaf spot incidence and severity of groundnut (Arachis hypogaea L.) In-vivo

Cercospora leaf spot diseases of groundnut (Arachis hypogaea L.) caused by Cercospora arachidicola and Cercosporidium personatum is an important disease that has the potential to significantly reduce the economic value of the crop. A research was conducted to determine the incidence and severity of the disease in four groundnut accessions: ICIAR-19BT, NGB01293, NGB00157 and NGB01294 grown in Abeokuta. Field experiments were conducted to determine the effect of aqueous extracts of these plants on incidence and severity of Cercospora leaf spot disease in split-plot fitted into a Randomized Complete Block Design with three replicates. Data obtained were subjected to Analysis of Variance and means were separated using Duncan’s Multiple Range Test at 5% level of probability. The results showed that groundnut accessions were infected by Cercospora leaf spot disease. Range of disease incidence was between 45.6% (NGB01293) and 63.4% (ICIAR-19BT) at 8 Weeks After Planting (WAP). Disease was “very severe” (rating 5.0 on a scale of 1-5) in NGB00157 relative to 4.67 (ICIAR-19B) and 4.0 (NGB01294) at 11 WAP. All tested aqueous extracts significantly (p ˂ 0.05) reduced the incidence and severity of Cercospora leaf spot disease on the field. Extract of C. odorata enhanced the lowest disease incidence (ranging from 15.0 to 10.0%) in the four accessions at 8 WAP while T. procumbens induced the lowest severity rating of 1.0 (on a scale of 1-5) in four accessions at 11 WAP. The study concluded that plant extracts can effectively control Cercospora leaf spot disease of groundnut and its causative organisms. However, T. diversifolia C. odorata and T. procumbens, should be used as a potential biocide in plant disease management, as they showed fungicidal and fungitoxic ability.