18 BULLETIN 995, U. S. DEPARTMENT OF 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 destined, 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. 



