Appraisal of antifungal potential of chemicals and plant extracts against brown leaf spot of soybean caused by Septoria glycine

Soybean is a legume crop originating in China. Its nutritional value, characterized by high-quality protein and unsaturated fats, makes it an excellent cholesterol-free diet option. Brown leaf spot of soybean, caused by Septoria glycine, is one of the most devastating diseases, resulting in significant yield losses. This study aimed to evaluate the effectiveness of new chemical fungicides (Topsin-M, Recado, Evito, Polyram-DF, and Curzate-M) at concentrations of 50, 100, and 150 ppm, and phyto-extracts (neem, clove, eucalyptus, ficus, and datura) at concentrations of 3, 5, and 7% against S. glycine under in vitro conditions. The most effective treatments from the in vitro tests were further investigated under greenhouse conditions using a completely randomized design with three replications per treatment. The results indicated that, among the fungicides, Topsin-M showed the lowest mycelial growth (3.5, 2.73, and 2.34 mm) at concentrations of 50, 100, and 150 ppm, respectively. Among the phyto-extracts, clove demonstrated the most effective results, with the least fungal growth (3.95 mm) at 7% concentration. Under greenhouse conditions, the best results were achieved with a combination of Topsin-M and clove, resulting in the lowest disease incidence (10.27%), followed by Topsin-M (17.65%) and clove (26.76%). This study suggests that new chemical fungicides and phyto-extracts can be effectively used as part of an integrated management strategy against brown leaf spot of soybean.