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''Phytophthora nicotianae'', commonly referred to as black shank is a plant pathogen infecting many hosts including tobacco,〔(Black shank ) American Phytopathological Society (APS)〕〔(Black shank of tobacco in the former Dutch East Indies, caused by Phytophthora nicotianae ): Original papers by Jacob van Breda de Haan, 1895 and Thung Tjeng Hiang, 1931 & 1938 Jan C. Zadoks Sidestone Press, Dec 15, 2014 page 163, 164〕 onion and strawberries. The oomycete first appeared in the United States in 1915.〔(Black Shank )〕 It was studied at the Deli Company tobacco plantation in Sumatra in the late 19th century〔 Black shank causes rapid yellowing, wilting and death of tobacco plants. It appears first as a dark brown or black lesion on the stalk at or near the ground level and extends upwards over time, also blackening the pith. The Phytophthora parasitica var. nicotiana pathogen lives in moist soil. Crop rotation is helpful in alleviating it.〔(Black Shank ) North Carolina State University Plant Pathology Extension〕 == Disease of onion == On ''Allium cepa'' it causes the disease known as phytophthora neck and bulb rot. Susceptible onion plants that are infected with this pathogen could easily die. Host resistance has been identified in short, mid-, and long day onions. Different stages of onion may be affected. Initially, tips of newly infected plants start yellow and dry followed by softening of the "neck" of the plans that eventually fall over. Infected leaves may show grey leaf lesions. Conditions that promote the development of this disease are warm and wet conditions. Use of resistant varieties is probably the best mode of control. Application of fungicide may reduce crop loss cause by Phytophthora neck and bulb rot. Irrigation, recirculation of water irrigation, flooding, and run-off could exacerbate the problem. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phytophthora nicotianae」の詳細全文を読む スポンサード リンク
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