Sugar Beet Root-louse 



Irrigation 



It has been shown by Mr. J. R. Parker of the Montana Experiment 

 station*, that the sugar beet root-louse does not multiply so rapidly in 

 moist as in dry soil. Experiments conducted by him on The Great 

 Western Sugar Company's farm at Edgar, Montana, and on the Gov- 

 ernment Reclamation Project at Huntley, Montana, show that fields 

 irrigated during the migration of the lice from the cotton -wood 

 trees to the beet fields are much freer from root-lice at harvest 

 than fields not irrigated until later. 



Migration begins about the 10th of June and is at its height about 

 the 20th of the month in the latitude of Denver, Colorado. In the lati- 

 tude of Billings, Montana, the height of migration is probably reached 

 six to eight days later. Since the losses due to this insect are propor- 

 tional to the number of lice present and feeding on the crop, anything 

 which reduces their number reduces the loss as well. Frequent irriga- 

 tions during the growing season reduce the infestation and also increase 

 the yield of beets. 



In a leaflet issued by Mr. Parker and circulated by The Great West- 

 ern Sugar Company at Billings, Montana, the results of several years' 

 work in the control of the sugar beet root-louse, show that there are 56.2, 

 46.6 and 25.6 beets out of every 100 infested where two, three and five 

 irrigations respectively were applied. 



The sugar content was 15.8%, 17.1% and 17.2% for two, three and 

 five irrigations respectively. 



The gross returns per acre were $82.27 for two, $85.61 for three, and 

 $96.07 for five irrigations. 



To some, early irrigation may seem like "jumping from the frying 

 pan into the fire, " since it is quite generally believed that early watering 

 is detrimental to sugar beets. Quite to the contrary it has been found 

 that irrigating as early as June 22nd produces better results in yield and 

 per cent of sugar in the majority of years. It is a fortunate coincidence 

 that early irrigation gives best results in just the years which are favor- 

 able for the development of root-lice; i. e., years when the winter and 

 early summer are dry. 



Through experiments conducted on The Great Western Sugar Com- 

 pany's Experimental Farm at Longmont, Colorado, it has been found 

 that, as an average of six years tests, irrigating as early as June 22nd to 

 25th has produced a yield of 14.66 tons per acre and 16.05% sugar, while 

 beets irrigated the first time July 5th to 10th gave a yield of but 14.23 

 tons per acre and a sugar content of 15.84%. Both the early and late 

 irrigated beets were watered three times each season. The gross re- 

 turns were $87.29 per acre for the early and $83.80 for the late 

 irrigated beets, without any greater expenditure of labor or water 

 for the increased returns due to early irrigating. 



Fall and Spring Irrigation; Plowing 



Fall or early spring irrigation will no doubt destroy most of the lice 

 in the soil. However, if the destruction of the lice is the only reason 



Vol 7*No' fe i U914) y f thC Sugar " beet Root - louse - Pemphigus betae" Journal of Economic Entomology. 



56 



