Sugar Beet Root-louse 



for this irrigation it is doubtful if the results will warrant the use of the 

 water. During the process of plowing and working down the seed bed, 

 the majority of the hibernating lice are destroyed. 



Rotation 



While quite a number of lice live over from season to season in the 

 soil of old beet fields, yet they are of little importance as compared with 

 the lice from the narrow-leaf cottonwood trees as a source of infesta- 

 tion. For this reason rotation is of very little avail in preventing 

 losses. The results of a survey covering 80,000 acres, made in 1916, 

 showed that 83 beets out of 100 were infested with root-lice where sugar 

 beets were grown on old beet ground and 82 out of 100 where they fol- 

 lowed all other crops. This proves conclusively that rotation will not 

 prevent root-louse losses. The presence of lice in the soil in the spring 

 is no reason why such fields should not be planted to beets provided 

 they are otherwise fit. 



The results of the survey mentioned above show quite conclusively 

 that the destruction of all narrow-leaf cottonwood trees within the beet 

 growing sections will reduce the damage done by the sugar beet root- 

 louse. Therefore, the cutting of these trees is strongly to be recom- 

 mended. However, it will not entirely free beet fields of this pest, since 

 many lice reach them from the foothills and canyons. 



DESCRIPTION AND LIFE HISTORY 



Mention has already been made of winged lice on the beet roots in 

 the fall. During warm, sunny autumn days swarms of these little 

 winged lice leave the beet fields and fly to the narrow-leaf cottonwood 

 trees. 



About every narrow-leaf cottonwood with the rays of the sun 

 glistening on their wings, thousands of lice sway in and out among the 

 branches. One by one they alight to go hurrying up and down as if 

 fearful lest the oncoming winter overtake them before suitable homes 

 for their young have been found. 



In deep crevices and under loose pieces of bark these winged migrants 

 from the beet fields deposit their minute, yellowish young. These are 

 of two kinds, tiny little females (Fig. 18, Plate II, Page 13), and still 

 smaller males (Fig. 16, Plate II). (Note the minute representation of 

 the actual size of these lice, shown at the left of the figures.) Almost 

 microscopic in size, mouthless and living but a few days, their sole object 

 in life is to produce the solitary egg which each female lays. This accom- 

 plished the female dies, the male having died shortly after mating took 

 place. 



Figure 13, Plate II, Page 13, is the antenna of Figure 16, Plate II, 

 Page 13, greatly enlarged. 



The eggs, one of which is shown very much enlarged (Fig. 17, Plate 

 II), are about fa of an inch long and one-fourth as broad. Snugly 

 tucked away in some crevice of the bark they remain until the warm 

 days of spring cause the buds to swell, when from each egg a small, dark 

 louse (Fig. 2, Plate II, much enlarged) emerges. As soon as hatched 

 this little louse starts in search of an opening bud. When one is found 



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