304 FUNGOUS DISEASES OF PLANTS 



Control. Wherever careful spraying experiments have been made 

 it has been found possible in ordinary seasons to reduce the injuries 

 from the early blight to a very small minimum by the same method 

 which has been recommended in case of the late blight and rot. 



XIV. ONION MOLD 

 Macrosporium Sarcinula Berk. 



MIYABE, K. On the Life-History of Macrosporium parasiticum Thiim. Ann. 

 Bot. 3: 1-26. pi. i. 1889. 



This fungus has long been associated with the onion mildew, 

 and by some pathologists it is supposed that it is commonly pres- 

 ent on diseased onions as a fungus of secondary importance. In 

 many cases it unquestionably follows the Peronospora of this host, 

 but in other cases it seems to be the direct cause of spots which 

 may involve the seed stalks, or which may occur upon the older 

 leaves and sheaths. It occurs in Europe, in the Bermudas, in the 

 northeastern United States, and possibly throughout a wider range. 

 It is conceivable that the fungus follows injuries of one sort or 

 another, such as those of thrips or other insects, as well as the 

 effects of the Peronospora, but it does not appear to be restricted to 

 plants infested by the last-mentioned fungus. In the case of onions 

 grown for seed it is especially injurious, since the seed stalks af- 

 fected seldom mature their product. Miyabe established the genetic 

 connection between the Macrosporium of onion and Pleospora her- 

 barum (Pers.) Rab., incidentally indicating, also, that the Macrospo- 

 rium agrees with the saprophytic form described by Berkeley. 



XV. MACROSPORIUM: OTHER SPECIES 



Occurring upon other solanaceous hosts are such species as 

 Macrosporium tomato Cke. and Macrosporium Datura Fautr. 

 Several species have been reported upon onions besides Macro- 

 sporium Sarcinula Berk, above discussed. Other species of 

 Macrosporium besides the latter have also been connected with 

 species of Pleospora. 



Macrosporium nigricantium Atkinson, Macrosporium Tabaci- 

 num Ell. & Ev., and Macrosporium Iridis C. & E. are commonly 

 reported as leaf spot or blight fungi of their respective hosts, cot- 

 ton (Gossypium), Iris, and tobacco (Nicotiana Tabacum). 



