Oct. i. i 9 *o Fusarium-B light (Scab) of Wheat and Other Cereals 1 1 



saubinetii, thus confirming results obtained by Hoffer, Johnson, and 

 Atanasoff (j) in 191 8, when it was demonstrated that the hyphae present 

 in the previously infected heads or cornstalks remain viable till spring, 

 when they form new conidia and thus help the further propagation of 

 the fungus. 



ASCOPORES 



Whenever the cause of the disease is one of the species having a perfect 

 stage, as is the case with Gibberella saubinetii, the perithecia of this fungus 

 are produced in great number on all infected parts, but especially on 

 the pseudo-plectenchymatic structures, on which there has been more or 

 less formation of conidia. Perithecia are formed on seedlings and in- 

 fected kernels (observed only under greenhouse conditions), on the straw 

 and the heads of the various cereal crops, and on the stalks, sheaths, 

 and ears of corn. The ascospores play an important role in the life of 

 this organism, since they are likely to resist extreme weather conditions 

 and furnish inoculum for the first infection in the spring. 



DISSEMINATION OF SPORES 



The experimental work on this subject is limited to a study of the 

 agency of wind, and to some extent of rain, in distribution of conidia. 

 Other factors may also play some role in the dissemination of conidia 

 and ascospores, but time did not permit a study of other factors. 



BY WIND 



In a rye field slightly infected with blight, numerous spore traps l 

 were placed on stakes in vertical and horizontal positions, some on the 

 ground and some at various heights, ranging from 3 to 8 feet above the 

 ground, and exposed from 12 to 24 hours, then examined under the 

 microscope. The number of Gibberella saubinetii conidia caught was 

 very small when compared with the number of spores of other fungi, 

 especially rust spores, that was found on each spore trap. Gibberella 

 saubinetii conidia varied in number from none to eight on the traps set 

 closest to the ground and especially on those placed vertically and fac- 

 ing the prevailing wind. Most of the conidia of Gibberella saubinetii were 

 caught by the traps set on the ground. The statement that the conidia of 

 species of Fusarium are wind-borne is not new. Saito (7) , studying the at- 

 mospheric flora of Tokyo, found that Fusarium conidia are carried by the 

 air in small number. The same fact has been reported by a number of 

 other workers. 



That the ascospores of Gibberella saubinetii are also wind-borne is 

 shown by the following observations in the field. One of the rye fields 

 under observation in 191 8, consisting of several acres, was located on 



1 Common microscope slides were covered with a layer of glycerin, or glycerin with some vaseline, and 

 were used as spore traps. 



