594 MICROBIAL DISEASES OF PLANTS 



is clouded and becomes lime-green in color after ten dayis. On potato it produces 

 a characteristic transient dark-blue green color which develops promptly and dis- 

 appears on the sixth day or earlier. Growth develops readily in XJschinsky's and 

 Fermi's solutions changing them to a pale green color in three to five days; faint 

 growth occurs in Cohn's- solution. Plain milk is cleared without coagulation, the 

 cleared fluid becoming a pale turtle-green color; litmus milk becomes deeper blue. 

 Gas is not produced from the ordinary sugars in Dunham's solution. Nitrates . 

 are not reduced, and some indol is formed. 



Method of Infection. — Inoculation experiments indicate that infection may take 

 place either through the stomata or through wounds produced by mechanical 

 injury. 



Control. — No control measures have been reported. 



Blight of Mulbeeky 

 Pseudomonas mori — Boyer and Lambert (Smith) 



History. — The disease was first sttidied in 1890 by Cubohi and 

 Garbini in Italy, and later by Boyer and Lambert in France who 

 named the causal organism Bact. mori, but did not describe it. In 

 igo8, Erwin F. Smith* found a similar disease in some of the Southern 

 States, and described the causal organism. 



Symptoms. — According to Erwin Smith, the blight attacks the 

 leaves and young shoots of the mulberry, producing first water-soaked 

 spots, which later become sunken and black; "foliage more or less 

 distorted; shoots soon show sunken black stripes and dead terminal 

 portions. Action of disease rather prompt." In very young shoots, 

 wood, pith and bark are invaded by bacteria; in older shoots the germs 

 are confined mostly to the xylem. 



Causal ORGANisM.^The organism is a rod with rounded ends, 3.6/1 by i.2m, 

 motile by 1 to 2 polar flageUa, attached to one end. No spores observed; pseudo- 

 zoogloea occur. Stains readily with carbol fuchsin; Gram-negative. 



On agar, spreading, smooth, dull, translucent, shiny, white; medium not stained. 



On potato, spreading glistening, smooth, white to dirty white, shiny, medium 

 grayed, slight action on starch. Gelatin stab, filiform, no liquefaction. Beef broth, 

 pellicle, strong clouding. Milk, no coagulation, rendered alkaline, becomes clear by 

 solution of fat and casein, litmus not reduced. No growth or scant in Cohn's 

 solution. Uschinsky's solution, copious, pellicle, not viscid fluid, bluish-fluorescent 

 color. No gas from dextrose, saccharose, etc. Aerobic. No indol or slight. 

 Nitrates not reduced. Thermal death-point 51.5°; does not grow at 37°. 



* Erwin F. Smith, Bacterial Blight of Mulberry, Science N S., Vol. XXXI, 803. 



