Cereals 299 



affected surfaces, sometimes so abundant as to lend a blackish 

 hue to the leaf, comprise the diagnostic symptoms of this 

 malady. Eventually the leaves are killed. 



Blight ^^^' ^^'' (Pseudomonas avence Manns). — A disease 

 prevalent throughout the Eastern and Central States was 

 attributed to bacteria by Galloway and South worth in 1890. 

 It appears when the plants are only about 10 cm. high, first 

 causing the leaves to turn brown and die at the tips, then 

 throughout their length. The affected plants revive, but 

 are so reduced in vigor as to prevent effective stooling, and 

 a loss of from 35 to 75 per cent of the crop commonly 

 occurs. 



The disease was carefully investigated by Manns, who 

 claims that it is caused by the symbiotic action of two species 

 of bacteria, a Pseudomonas and a Bacillus. 



Manns describes the disease as follows: 



The preliminary effect is yellowing of the leaf, beginning 

 either as small, round lesions on the blade, or as long, streak- 

 like lesions extending throughout the blade and even the 

 whole length of the culm and blades. Occasionally it begins 

 at the tips and works back into the culm; again the upper 

 leaves often break down due to a weakened condition of 

 the plant from defoliation below. 



The ultimate symptoms, wherever the disease has made 

 much progress, are partial or general collapse of the leaves, 

 which take on a mottled to almost red color. 



It prevails from New England to Georgia, and from the 

 Atlantic to Indiana and Illinois. The damage in Ohio has 

 been estimated at from 14 to 37 per cent of the crop. Rain 

 and moisture favor it. 



When prevalent, the soil may become infested as in typical 

 soil diseases. The only hope seems to rest in resistant 

 strains. 



Halo-blight (Bacteria). — Oval, chlorotic areas 1-2 cm. in 

 diameter, bordering a minute, sunken, dead center, occur 

 in the leaf. Stripe-blight (Bacteria). — The diseased tissues 

 are water-soaked, translucent, with an abundant exudate and 



