250 Journal of Agricultural Research voi. iv, No. 3 



because of the mistaken idea that if the fields are allowed to dry out the 

 sugar-beet plant will send its taproot deeper into the soil in search of 

 moisture and thus produce a better-shaped beet. Extremely dry con- 

 ditions at this time not only check the growth of the plant but offer ideal 

 conditions for the starting of root-louse colonies. The ground is generally 

 cracked open about the base of the plant and the young lice deposited 

 upon the leaves by the migrants have no difficulty in establishing them- 

 selves upon the fiber rootlets in the comparatively dry soil, where all 

 conditions are favorable for rapid growth and multiplication. Fortu- 

 nately the best authorities on sugar-beet culture are urging against allow- 

 ing the beet fields to become dry at this time, not primarily because of the 

 possibility of root-louse infestation, but because of the general welfare of 

 the crop. Mr. Hans Mendelson, scientist for the Billings Sugar Co., has 

 stated to the writer several times that all of that company's irrigation 

 experiments have shown that early and frequent irrigations produce the 

 highest sugar content and tonnage. In a recent letter he states, "All 

 our experiments in early irrigation have shown that irrespective of aphis 

 it is the right treatment." Thus, by irrigating early, before the fields 

 become dry, the chances for root-louse infestation are reduced and the 

 best conditions for plant growth are secured. 



It is also important that plenty of soil moisture be maintained through- 

 out the growing season. Some of the myriads of young lice produced by 

 the migrants from the cottonwoods are almost sure to become established 

 even in fields that are well irrigated. The presence of sufficient soil 

 moisture will tend to retard their increase and by promoting a vigorous 

 plant growth will enable the sugar beets to withstand better the root- 

 louse attacks. A scarcity of soil moisture results in a rapid multiplication 

 of the few root lice that may be in the soil, and plants suffering for lack 

 of moisture are in very poor condition to withstand the drain of root- 

 louse attacks. 



The details of this system, such as the number of irrigations per season, 

 the quantity of water to be applied at one irrigation, and the question 

 of cultivation, have not been thoroughly worked out, and the problem 

 will demand several seasons' work before definite recommendations can 

 be made. However, the principle is believed to be sound, and at present 

 irrigation apparently offers the most effective and the most practical 

 method of controlling the sus^ar-beet root louse. 



