THE BEET-SUGAR INDUSTRY IN THE UNITED STATES. 17 
Diseases affecting stand. — One of the common agencies affecting 
the stand of sugar beets is disease. Nearly all of the sugar-beet dis- 
eases are due to parasitic organisms. One of the most serious 
affecting the stand is the damping-off of the young beets. Later 
in the season root-rot does considerable damage in some localities. 
Leaf -spot frequently injures the beets and reduces the tonnage, but 
does not often destroy the stand. All fungous diseases may be greatly 
reduced or entirely controlled by proper cultural methods, including 
the proper rotation of crops. There are several diseases which some- 
times destroy entire fields. The disease known as " curly-top " be- 
longs to the group. This is an obscure disease, the cause of which is 
not definitely known. The Office of Sugar-Plant Investigations in 
cooperation with the Bureau of Entomology is making an earnest 
effort to determine the cause of this disease and to find a practical 
means for its control. Another serious pest affecting the stand of 
beets is the sugar-beet nematode. The nematode first appears in a 
field here and there, destroying a few beets. From year to year this 
becomes more marked if beets are grown continuously in the infested 
fields, and eventually the whole field will be affected and a worthless 
crop will result. The Office of Sugar-Plant Investigations in coopera- 
tion with the Office of Agricultural Technology is carrying on ex- 
tensive experiments in all areas infested with the sugar-beet nematode, 
with a view to controlling this pest in a practical way, so that profit- 
able crops of beets may be grown in spite of the nematode. For a 
further discussion of sugar-beet diseases, see pages 44 to 47. 
Insects affecting stand.— -There are several insects affecting the 
stand of sugar beets. The most common during the early stages of the - 
beet are wireworms and cutworms. The latter usually cut off the root 
at some distance below the ground. As a result the plant dies or pro- 
duces a very short root. Sometimes the cutworms destroy beets here 
and there in the field, but when the pests are numerous the entire 
stand may be destroyed, necessitating replanting in order to produce 
a crop. White grubs also are serious pests. They are the larvae of 
the May and June beetles. They occur frequently in sod ground and 
are to be expected in beet fields where beets follow sod. Later in the 
season army worms and related pests frequently do considerable 
damage. Even if the stand is not seriously injured by the pests the 
tonnage is greatly reduced. For a further discussion of insect pests 
affecting sugar beets, see pages 47 and 48. For a list of publications 
relating to sugar-beet diseases and insects, see pages 55 and 56. 
Rodents affectmg stand. — In some localities ground squirrels and 
other rodents are a serious menace to the sugar-beet crop. They feed 
upon the beets from the seedling to the mature stage, but do most 
of their damage when the beets are about half grown. They some- 
63212°— 18— Bull. 721 3 
