46 BULLETIN 995, U. S. DEPARTMENT OF AGRICULTURE. 



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 

 schacMii). 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 soil 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 

 useless 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 numerous 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- 

 Qjst stage. In this stage the nematode is very resistant to unfavor- 

 able 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 determine the 

 proper length of the rotation with these resistant crops, so that the 

 nematodes will be reduced to such a small number that sugar beets 

 may be grown with profit in spite of the pests. Various soil treat- 

 ments 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 over all sugar-beet 

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



Curly-top. — The curly-top is confined to the western part of the 

 United States. So far as is known, it has not been seen in the east- 

 ern portion of the sugar-beet area or in any of the beet fields of 

 foreign countries. It has appeared in practically all States west of 

 Minnesota and IoAva where sugar beets are grown commercially, 

 although it has not been seen in all of the sugar-beet areas of the 

 West. It is not due to unfavorable climatic or soil conditions: nor 

 is it due to the kind or quality of seed used. It is connected in some 



