2 BULLETIN SKJ4, U. S. DEPARTMENT OF AGRICULTURE. 



While the parasites reported as causing damping-off are probably 

 not as numerous as the host species which are subject to it, a con- 

 siderable number are known. Two quite different types of damping- 

 off parasites may be recognized. In the first type we have fungi, 

 such as Pythium debaryanum Hesse and Cort'ic'mm vagum B. and C, 

 soil inhabiting and primarity saprophytic, which attack a great 

 variety of hosts, and are at least better known, if not more destruc- 

 tive, as damping-off organisms than as parasites on older plants. 

 They are specialized as to the type and age of tissues which they at- 

 tack rather than as to host. The second type includes fungi less 

 common as saprophytes and with a relatively limited, sometimes A T ery 

 closely limited, host range. PKoma betae, the systemic parasite of 

 sugar beet (37), is an excellent example of the host-specialized para- 

 site, transmitted in the seed and capable of seriously injuring various 

 parts of the older plant at different stages of growth as well as at- 

 tacking seedlings. 



Most damping-off parasites are intermediate in habit between the 

 extremes of these two types. Of those which are somewhat host 

 specialized, the following may be mentioned : 



Pliomopsis reruns, the cause of foot-rot of eggplant, reported by Sherbakoff 



(128) as a frequent cause of damping-off of this host and believed to be 



carried on seed. 

 Gibberclki saubinetii (Mont.) Sacc. (29) and the imperfect fungi which kill 



grain seedlings as well as cause diseases of the older plants (SO; 126, 



p. 218). Species of Gloeosporium and Volutella named by Atkinson (2, 



p. 269; 52) as able to kill seedlings or cuttings of particular host plants. 

 Glomerella (Colletotrichum) gossypii, described by Atkinson (1) and Barre 



(4) as likely to cause damping-off of cotton (112). 

 Fusariuiii lini, the flax parasite, reported by Bolley (14) as destructive .to 



young seedlings. 

 Phoma liitf/am. the cause of black-leg of cabbage, at least under inoculation 



conditions able to kill quickly seedlings of cabbage and other crucifers 



(72). 

 Peronospora parasitica (Pers.) De Bary, a downy mildew attacking cabbage 



and various other crucifers, reported as killing thousands of very young 



cabbage plants in Florida seed beds (41). 

 The entomnphthoraceous Completoria complcns, on fern protnallia (1; S7, 



p. 203). 

 Bacillus malvacearum, a parasite of the leaves of cotton plants, which can 



also cause damping-off of its favorite host (113) and the bacteria from 



diseased cucumber plants With which Halsted (53) caused typical 



damping-off of cucumbers. 



Damping-off fungi with wider host ranges include Phytophthora 

 f<i<ji. Apbanomyces levis (100), Rheosporangium aphamdermatus 

 (38, 39), Botrytis cinerca, and certain Fusaria. The so-called prop- 

 agation fungus, " vermehrungspilz," a sterile damping-off mycelium 

 which Sorauer (133, p. -"»2l) believed related to Sclerotinia and for 

 which Ruhland (115) has erected a new genus, considered by both 



