THE BEET-SUGAR INDUSTRY IN THE UNITED STATES. 47 
and Europe. One of these is known as Cercospora and the other 
as Phoma; the latter is the same fungus that produces the root-rot. 
When the spores of either of these fungi fall upon the beet leaves 
and the conditions are favorable the fungus growth attacks the tissue 
of the leaf, producing distinct and characteristic spots. The Cerco- 
spora fungus does not generally attack any part of the beet plant 
except the leaf blade and the petiole, while the Phoma may attack 
leaf and root. If these fungi are present in large numbers they may 
do considerable damage to the beet crop. If the attacks are severe 
early in the season, the growth of the beets is retarded and conse- 
quently the yield is reduced. If the attacks do not occur until late 
in the season, after the beets have practically reached their normal 
growth, the diseases will reduce the sugar without appreciably af- 
fecting the tonnage. If these fungi attack the beets in midsummer, 
both the }deld and the quality will be generally reduced. These 
diseases may best be controlled by deep fall plowing and by crop 
rotation. Crop rotation is especially recommended where it can be 
practiced, but in cases where it is necessary to follow beets with beets 
after these diseases have appeared, the ground should be plowed in 
the fall to a good depth, not less than 12 to 14 inches. In fact, all 
plant-pathological problems, from a practical standpoint, are closely 
connected with the cultural phases of crop production. Production 
can not be successfully studied without a knowledge of the diseases 
affecting that particular crop, nor can the disease of a crop be in- 
telligently considered with reference to control measures except in 
conjunction with the cultural practices and with a knowledge of the 
conditions under which that crop is grown. 
INSECTS. 
The principal insects affecting sugar beets have been treated in 
various publications of the Bureau of Entomology. A list of these 
publications is given at the end of this bulletin. Among the im- 
portant forms which affect the leaves are the webworms and the 
beet army worm. In some localities blister beetles, flea beetles, and 
local pests do considerable damage, mainly by destroying the foliage. 
They also have a retarding effect on the growth of the beet, but the 
principal injury is due to the destruction of the foliage and the con- 
sequent expenditure of energy and food required by the plant to 
produce a new set of leaves. Usually these insects start in small 
areas on one side or a corner of a field and spread rapidly. Of some 
species there are several generations in a season, and if weather con- 
ditions favor their development much damage is frequently done. 
In the case of insects working early in the season the tonnage of the 
beets may be greatly reduced, and if the insects continue until late 
