18 BULLETIN 995, U. S. DEPARTMENT OE AGRICULTURE. 
spot frequently injures the beets and reduces the tonnage, but does 
not often destroy the stand. All fungous diseases may be greatly re- 
duced or entirely controlled by proper cultural methods, including 
the proper rotation of crops. 
There are several diseases which sometimes destroy entire fields. 
The disease known as curly-top belongs to this 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 area becomes more marked if beets are 
grown continuously in the infested fields, and eventually the whole 
field is affected and the crop is worthless. The Office of Sugar- Plant 
Investigations in cooperation with the Office of Agricultural Tech- 
nology is carrying on extensive experiments in all areas infested with 
the sugar-beet nematode, with a view to controlling this pest in a 
practical way, so that profitable crops of beets may be grown in 
spite of the nematode. For a further discussion of sugar-beet dis- 
eases, see pages 45 to 48. 
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 produces 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 con- 
siderable damage. Even if the stand is not seriously injured by the 
pests the tonnage is greatly reduced. For a further discussion of in- 
sect pests affecting sugar beets, see pages 48 and 49. For a list of 
publications relating to sugar-beet diseases and insects, see pages 
57 and 58. 
Rodents affecting 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 sometimes 
make serious inroads upon the stand of beets. These pests may be 
destroyed by the use of poison or by trapping. 
