Gamma irradiation and its convergence with nano-silver particles and sodium dichloroisocyanurate (NaDCC) were investigated to inhibit germination and mycelial growth of Botrytis elliptica, the pathogen of lily leaf blight. In addition, the same treatments were studied on the process of disease development with detached leaf of lily cv. Siberia. Spray inoculation, which is closer to natural infection than wound inoculation, can be a way to investigate infection ability of the treated pathogen. The irradiating dose required to reduce the population by 90%, D₁₀, was 526 Gy irradiating with 0-2000 Gy gamma ray on the conidial suspension as well as the growing mycelia. Even at 2000 Gy, the mycelium was not killed but just delayed its growth at 1?2 days behind. Convergent treatment with 40 mg/l of NaDCC just before 200 Gy gamma irradiation was the best way to decrease the conidial germination about 1/1000 times. The control values of gamma irradiation were 23% and 19.5% at wound inoculation and spray inoculation, respectively. On wound-inoculation, the control value of NaDCC only was 89%, and that of NaDCC convergent with 200 Gy gamma irradiation was 32%. On sprayinoculation, the highest control value was NaDCC at 50%, and that of NaDCC convergent with gamma irradiation was 24%.