THE BEET-SUGAR USTDUSTRY 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 affectimg 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 



