Pathogens associated with Chinese kale leaf spot disease were recovered from necrotic lesions on the Chinese kale leaves and identified as Alternaria brassicicola (Schw.) Wiltshire. This disease is one of the most significant destructive pathogens to vegetable crops in Thailand and Southeast Asia. Disease management of these pathogens is done by using synthetic fungicides which are expensive and harmful to the environment. This study aimed to investigate the efficacy of the extracts from five plants, Hydnocarpus anthelminthicus Pierre ex Laness., Crateva magna (Lour.) DC., Caesalpinia sappan L.,Xanthophyllum lanceatum J. J. Sm., and Carallia brachiata (Lour.) Merr. to control the Chinese kale leaf spots caused by A. brassicicola in in vivo condition. In an in vivo test, we found that the plant extracts of C. brachiata, H. anthelminthicus, X. lanceatum and C. magna showed a potential in control efficacy against brassica dark leaf spots caused by A. brassicicola. The four plant extracts effectively suppressed the development of leaf spots at a concentration of 10,000 ppm and 50,000 ppm at 30 DAT. However, at 40 DAT the C. magna and H. anthelminthicus extracts strongly inhibited A. brassicicola at concentrations of 10,000 ppm and 50,000 ppm respectively when compared with the water control. This is the first report demonstrating that the plant extracts collected from riparian forest can provide control against brassica dark leaf spots disease. Based on our

study, we demonstrated that the ability of plant crude extracts can be used as natural fungicides to control Chinese kale leaf spots and replace synthetic fungicide.