June 15, 1915 Soil Moisture and Sugar-Beet Root Louse 



243 



into three lots and watered as follows : Lot i , subirrigated so as to keep 

 the top 2 inches of soil dry; lot 2, subirrigated so as to keep surface soil 

 slightly moist; lot 3, watered from above so as to keep soil very moist 

 throughout. At the end of two months all root lice that could be re- 

 covered were counted. The results are given in Table II. 



Table II. — Record of sugar-beet root-louse increase under different soil-moisture condi- 

 tions. Second insectary experiment 



In this experiment root lice living upon sugar beets in the driest soil 

 again showed the highest rate of increase, 100 increasing to 7,027 in two 

 months. 



Combining the data from the two insectary experiments, the following 

 statement may be formulated : 



200 sugar-beet root lice in rather dry soil increased in two months to 11,581. 

 200 sugar-beet root lice in rather moist soil increased in two months to 2,510. 

 200 sugar-beet root lice in very moist soil increased in two months to 405. 



FIELD EXPERIMENTS IN MONTANA 



During the summer of 191 4 experiments for the purpose of determining 

 the influence of irrigation upon the reproductive power of the sugar-beet 

 root louse were carried on at the following places in Montana: Huntley 

 Experimental Farm, Huntley, Yellowstone Valley; Montana Experiment 

 Station farm, Bozeman, Gallatin Valley; Billings Sugar Co.'s experimental 

 farm, Edgar, Clark Fork Valley. Very different conditions prevailed at 

 each place, and the experiments are therefore reported under separate 

 heads. 



IRRIGATION EXPERIMENT AT HUNTLEY 



Six one-tenth-acre plots of sugar beets located on the experimental 

 farm of the Bureau of Plant Industry at Huntley were used in the experi- 

 ment. Mr. Dan Hansen, farm superintendent, was directly in charge of 

 the experiment, and his hearty cooperation at all times is here acknowl- 

 edged. The plots were about 3 miles from the nearest cottonwood trees 

 {Populus spp.) and were, therefore, not in a position to become so heavily 

 infested as were the plots at Edgar, which were bordered by a cottonwood 

 grove. 



