Effect of Light to Sporangium Survival of Cucumber Downy Mildew

Effect of light under controlled to sporangium survival of cucumber downy mildew was investigated.The results showed that irradiated under Ultraviolet radiation for 4 h,fresh sporangia of P.cubensis would be killed and no sporangia were germinated.Exposure under the direct sun light for 2 h,the germination ratio of sporangia began decreased,more than 50% sporangia were killed after 4 h treatment under direction sunlight,and most sporangia were lost germination ability after 36 h irradiation under directly sun light.In natural conditions,sporangia began lost germination ability in darkness and the life-span was about 72 h in the conditions.Diffusion light or thin light was in favor of the survival of sporangia.The life-span of sporangia under diffusion light was longer than in darkness.The experiment results also showed that the short time irritation promoted the development of fresh sporangia and raised the germination ratio.