Ecology and Control of Phytophthora melonis in Drained Paddy Field

Abstract

Dry air current failed to remove tha sporangia of Phytophthora melonis from the disease lesions. However, the fungus was easily dispersed by its zoospores and sporangia carried in irrigation water or liberated to the air by wind-blown rainsplanshes. The soil moisture strongly influenced the survival of P. melonis. The fungus persisted only for 4 wks in flooded soil, while in soil with moisture content at 6% or 20%, a condition that permitted soil aeration, the fungus could be detected from the infested soil for a period of 5~20 wks. 胡瓜疫病菌 (Phytophthora melonis) 之游走子囊在病組織上不具脫落性，乾風無法將之吹落。但是它的游走子及游走子囊可隨灌溉水及飛濺的雨水傳播。土壤溼度強烈影響病原菌的存活，病原菌在淹水的土壤中僅能存活4星期，但在含水量6%及20%，稍可通氣之濕土裡，也僅能存活5~20星期。田間試驗顯示，在經過兩期水稻輪作的稻圃裡，胡瓜疫病菌不能存活。