Three mechanically transmissible viruses were isolated from a diseasedSolanum jasminoidesplant obtained from India. One is a strain of potato virusY, which in some potato varieties produces symptoms resembling those caused by potato virusC, but unlike potato virusCit is readily transmitted byMyzus persicae.The second, named tobacco wilt virus, is also transmitted byM. persicaebut much less readily, whereas the third, named datura necrosis virus, is not. All three have a wide host range, but neither tobacco wilt nor datura necrosis viruses infects potato plants. All three have long flexuous particles and similar general properties.Simultaneous infection with datura necrosis virus usually decreases the concentration reached by potato virusYin tobacco plants but not inNicotiana glutinosa.