Multiple choice Blank-shank of tobacco is caused by which of the following organisms? Rhizoctonia Phytophthora nicotianae Fusarium Pythium aphanidermatum Reveal answer Fill a bubble to check yourself B Correct answer Explanation Blank-shank or black shank of tobacco is caused by the oomycete Phytophthora nicotianae. It is a serious disease affecting tobacco plants, causing stem and root rot.