502 JOURNAL OF ECONOMIC ENTOMOLOGY (Vol. 9 



makes the manufacture of sugar at a profit impossible if the sugar 

 per cent drops below a certain level. 



In order to ascertain the effect of the beet root-louse upon the per- 

 centage of sugar in the beets a series of 61 five-beet samples was taken 

 during the second week of September 1912. All of these samples 

 came from an area not to exceed 20 square rods in extent. Thirtj^-one 

 of these samples were made up of beets free or nearly fi-ee of root-lice, 

 the remaining thirty being made up of beets which were infested but 

 not to a degree sufficient to effect their appearance. The uninfested 

 samples averaged 14.62 per cent sugar. The lowest sample tested 

 12.9 per cent and the highest 15.3. The infested samples tested 13.85 

 per cent as an average and ranged from 11.7 per cent to 15.7. The 

 difference in favor of the uninfested samples was 0.77 of 1 per cent in 

 sugar content and 2.11 per cent in apparent purity. 



Again in 1914 a similar test was made. This time 40 samples were 

 taken, 20 infested and 20 uninfested. The former averaged 13.12 

 per cent sugar, the individual per cents ranging from 11.2 to 16.9 per 

 cent. The latter averaged 14.06 per cent with a range of from 12.2 

 to 16.8 per cent sugar. Of the infested samples but one was above 

 14.4 per cent while of the uninfested there were 6 above this point. 

 The uninfested samples averaged 0.94 of 1 per cent higher than the 

 infested. 



In weight the infested samples averaged 4.98 lbs. The heaviest 

 sample weighed 6.5 lbs. and the lightest 3.5 lbs. The average weight 

 of the uninfested samples was 6.7 lbs. The heaviest weighed 9 lbs. 

 and the lightest 5.5 lbs. It is a well-known fact that among beets 

 grown under the same conditions the large ones average lower in per 

 cent sugar than the small ones. This being the case the small infested 

 beets should have contained a higher per cent of sugar than the larger 

 uninfested ones had not the effect of the lice been the cause of the 

 lower weight as well as sugar content. Figuring from the above and 

 assuming that we have a perfect stand of beets which would mean a 

 beet every foot in the row and the rows 20 inches apart or 26,000 beets 

 per acre the lice reduced the yield 4.55 tons per acre. However, not 

 more than 50 per cent of the beets of a field could safely be considered as 

 infested to this degree in the average. This would mean that the loss 

 really was not far from 2.25 tons per acre as a result of the root-lice. 



At an average price of $5.80 per ton this means a direct loss of $13.05 

 to the grower, without taking into consideration the loss in sugar per 

 cent. 



Control Measures 



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

 Station, that irrigating at the time the spring migrants of the root- 



