Pests and Diseases ‘199 
only a few years and the diseases have required time for 
their spread. New beet areas have each year been 
opened up and these have been free from disease. The 
American beet-raiser has come to regard the crop as being 
free from disease and requiring no attention in this mat- 
ter. The time of complete freedom from disease, however, 
has passed. Already the fields in the older districts are 
infested ; the fight must be taken up in earnest. We may 
feel thankful for past immunity, but now precautions must 
be taken to keep in check the diseases that menace the 
industry. Many fungous and bacterial organisms live on 
the sugar-beet plant, but only a few are of great economic 
importance. There are also a number of troubles that 
seem to be physiological. Forms of rot on tubers in stor- 
age are shown in Plate XXIII. 
Leaf-spot (Cercospora beticola Sacc.). 
This fungous disease is one of the best known and 
widely distributed of the sugar-beet. It is found in all 
American beet-growing districts. The amount of injury 
depends on the number of the fungous plants present 
and the period in the beet’s life when the attack begins. 
Late plantings are as a rule less affected by the disease 
than early. It is more injurious to sugar-beets than to 
the red garden variety. 
It begins as tiny white spots scattered over the leaf, 
which later develop into small brown spots with a red- 
dish purple margin. There may be from ten spots to 
several hundred on each leaf. As the spots become older 
they turn ashen gray at the center and gradually increase 
in size until the entire leaf may be covered, when it he- 
