246 



Journal of Agricultural Research 



Vol. IV, No. 3 



were irrigated for the purpose of keeping the soil fairly moist at all 

 times. To accomplish this, water was applied three times: July 3, 

 August 10, and August 25. Cultivations were given as follows: June 17, 

 June 30, July 8, and July 20. Two alternate plots were allowed to 

 become quite dry and were irrigated only once during the summer: 

 August I o. They were cultivated on June 1 7 and July 2 2 . On October 1 8 

 each beet was examined for root lice, as in the Huntley experiment. 

 The combined results from the four plots are given in Table VI. 



Table VI. — Record of sugar-beet root-loiise increase under different soil-moisture con- 

 ditions. Bozeman irrigation experiment 



Not a beet in any of the plots was injuriously infested at the time of 

 harvest. It is hard to understand why the infestation in all plots was 

 so slight, unless we take into consideration the factor of rainfall. Fre- 

 quent rains during September and early October kept all the plots quite 

 wet and may have resulted in killing many of the lice. 



The experiment, however, showed a marked difference in the number 

 of slightly infested plants on the wet and the dry plots. In the plots 

 irrigated only once 48.6 per cent of the plants were infested, while in 

 the plots irrigated three times the infestation was reduced to 8.8 per 

 cent. 



IRRIGATION EXPERIMENT AT EDGAR 



Four plots, each containing 0.45 acre, were used. They were located 

 on the Billings Sugar Co.'s experimental farm and were in charge of Mr. 

 Hans Mendelson, whose friendly cooperation made the experiment at 

 this place possible. 



The plots were bordered by a grove of cottonwoods, in which many of 

 the trees bore thousands of galls of the sugar-beet root louse, and during 

 the summer migration period the winged lice could be seen flying in large 

 numbers from the trees to the beets. Upon some plants as many as 8 

 migrants were seen at one time. Each migrant on an average produces 

 10 young, which descend to the beet roots; and, when it is stated that 

 in insectary experiments 10 lice have been known to increase to 2,150 

 in two months, it can readily be understood why the infestation was so 

 severe. 



The rainfall from June 15 to September 30 is given in Table VII. 



