BLIGHTS. 495 



or reddish border. These blisters are filled with myriads of bacteria, 

 and in time, they dry down, forming a pale yellow or amber- colored crust 

 over the affected areas. Ultimately the diseased leaves become brittle, 

 ragged, and are worthless, while the pods curl, shrivel, and rot. 



METHOD OF INFECTION. It is believed that the disease is introduced 

 with the seed, and when once established, is spread from plant to plant 

 by rain, dew, and leaf-eating insects. 



CAUSAL ORGANISM. Ps. phaseoli Smith,* is a short, motile rod with rounded ends, 

 which produces a characteristic yellow growth on the different culture media. Gelatin 

 slowly liquefied. Milk becomes slowly alkaline, casein is precipitated by lab ferment 

 and partially redissolved. Very marked diastatic action on potato starch. No gas 

 from glucose, saccharose, etc. Aerobic. Uschinsky's solution, growth feeble and 

 retarded. Thermal death-point 49.5. 



CONTROL. Care should be taken to select seed from healthy fields 

 where the disease has never occurred. The disease has been partially 

 controlled by spraying with Bordeaux mixture when the plants were 

 2 to 3 inches high, again ten days later, and after blossoming. 



BLIGHT OF MULBERRY. 

 Bacterium mori Boyer and Lambert (Smith). 



HISTORY. The disease was first studied in 1890 by Cuboni and 

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

 the causal organism Bad. mori, but did not describe it. In 1908, Erwin 

 F. Smithf 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 dis- 

 torted; 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 1.2 fjt, motile 

 by i to 2 polar flagella, 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. 



* Smith, Erw.t Proc. Am. Asso. Adv. Sci., 46, 228-290, 1897. 



f Erwin F. Smith: Bacterial Blight of Mulberry, Science N. S., -Vol. XXXI, 803, 



