向日葵霜霉病Plasmopara halstedii是一个经济上相当重要的,种传和土传的毁灭性病害。在有利的气机条件下,它能致使田间植株枯死70—80％,并严重降低种子发芽。此病在南、北美州、欧州和苏联的大面积生产地区,具有特别毁灭性。生物学霜霉病本身表现出不同症状,它能引起猝倒、矮化、叶子局部病症,根和茎基 Sunflower Downy Mildew Plasmopara halstedii is a devastating disease that is economically significant, bred and transmitted. Under favorable gas turbine conditions, it can cause 70-80% of the plants to die in the field and severely reduce seed germination. The disease is particularly devastating in large-scale production areas in South, North America, Europe and the Soviet Union. Biological downy mildew itself manifests itself with different symptoms that can cause cataplexy, dwarfing, leaf topography, root and stem base