Selection of the Antibacterial Agents for Control Against Pseudomonas syringae pv. syringae causing Leaf Spot Disease on Green Pumpkin (Cucurbita moschata)

Bacterial leaf spot, caused by Pseudomonas syringae pv. syrinage, is a very damaging disease togreen pumpkin in Gong-ju and Non-san nursery. However, there is no good method to control the disease inKorea. Growth inhibition of pathogen on medium, control efficacy on seedling stage, and seed treatmenteffect of 6 anti-bacterial pesticides were investigated for selection of the best pesticide for seed treatment andcontrol of the disease. Growth inhibition zone on King’s B medium were the largest by oxytetracycline170 ppm and oxytetracycline 15 ppm + streptomycin sulfate 188 ppm, oxolinic acid 200 ppm, streptomycin200 ppm were next respectively. Control efficacy of oxytetracycline 1.5% + streptomycin sulfate 18.8% WPand oxytetracycline 17% WP on seedling stage were 71.4% and 49.4%, respectively. Seed treatment ofoxytetracycline 15 ppm + streptomycin sulfate 188 ppm on the artificially inoculated seeds inhibits pathogengrowth completely from the treated seeds and 96% control efficacy on grow-out test of the treated seeds.Seed treatment of streptomycin 100 ppm (2,000 dilution of streptomycin 20%) on the artificially inoculatedseeds allow 280 cfu/g of pathogen growth from the treated seeds and 60% control efficacy on grow-out testof the treated seeds. Seed treatment of oxytetracycline 85 ppm (2000 dilution of oxytetracycline 17% WP) onthe artificially inoculated seeds allow 80 cfu/g of pathogen growth from the treated seeds and 90% controlefficacy on grow-out test of the treated seeds. These results suggested that oxytetracycline 1.5% +streptomycin sulfate 18.8% WP was the best pesticide for seed treatment to control of the bacterial spotdisease by Pseudomonas syringae pv. syringae. Key words Bacterial leaf spot, Green pumpkin, Pseudomonas syringae pv. syringae, Seed treatment