THE BEET-SUGAR INDUSTRY IN THE UNITED STATES, 45 



widespread, so that the stand is seriously injured, the field should 

 be disked and replanted. Damping-off is more common in the early 

 spring, when the ground is damp and not thoroughly warm, but the 

 disease will not occur unless one of the damping-off organisms is 

 present. 



Nematodes. — ^The sugar-beet nematode is a minute wormlike or- 

 ganism, sometimes called an eelworm, which attaches itself to the 

 root and when present in sufficiently large numbers retards the growth 

 of the beet. There are several species of the nematode which attack 

 the sugar beet, but only one is considered especially serious; hence, 

 this species is known as the sugar-beet nematode {Heterodera 

 schachtii). This pest has been known for many years in Europe 

 and has existed in isolated localities in this country for more than 

 a decade. It is spreading, both by its own activity in certain stages 

 of its existence and by being carried from the present infested areas 

 by various agencies. The pest lives in the Loil from year to year and 

 travels slowly, so that the infested area is gradually increased, until 

 frequently an entire field or even a group of fields may become use- 

 less from the standpoint of beet production. Unfortunately, this 

 pest will attack many plants besides the sugar beet. This makes 

 it extremely difficult to control by crop rotation, which is one of 

 the best methods known for the control of many of our plant pests. 

 However, there are a number of plants that the nematode attacks 

 to a very slight extent or not at all. Again, the nematode passes 

 through several stages of development; one of these is known as 

 the brown-cyst stage. In this stage the nematode is very resistant 

 to unfavorable conditions and will remain alive in the soil for a 

 number of years ; the exact length of time is not known. The Office 

 of Sugar-Plant Investigations is making every effort to determine 

 the crops that are resistant to the nematode under the local soil 

 and climatic conditions where the nematode exists and also to deter- 

 mine the proper length of the rotation with these resistant crops, 

 so "that the nematode will be eradicated or at least reduced to such 

 a small number that sugar beets may be grown with profit. Various 

 soil treatments also are being tested on nematode-infested areas. 

 Some of these tests are very promising but will need to be repeated 

 - before anything definite can be said regarding their beneficial effects. 

 Careful surveys have been made in some of the infested areas, and 

 all fields or spots in fields containing nematodes have been listed 

 and marked, either for study or for the purpose of growing crops 

 other than sugar beets on them. A similar campaign is planned in 

 the other infested areas where the sugar-beet nematode has gained 

 a foothold, while a careful watch is being kept overfall sugar-beet 

 areas in order to detect and combat the pest on its first appearance. 



Curly-top. — This disease of the sugar beet is confined to the west- 

 ern part of the United States. So far as is known, it has not been 



