12 MONTANA BULLETIN 150 



County 1920 1921 1922 



Glacier (eastern section) 35.0 



Hill 25.0 33.0 7 



Jefferson 36.0 12.0 



Liberty 47.1 50.0 3 



Phillips 16.9 0.0 



Prairie 6.5 



Teton 29.0 7.0 



Toole 50.0 33.0 



Yellowstone 2.0-5.0 



It will be seen that in 1921 marked reductions took place in 

 Broadwater, Chouteau, Jefferson, Teton, and Toole counties and that 

 in one county, Phillips, which had a loss of 16.9 per cent in 1920, 

 there was no cutworm damage at all in 1921. This was also true of 

 Valley and Roosevelt counties which suffered considerable loss in 1920 

 but none since that time. The counties in which the cutworms held 

 their own in 1921 were Cascade and Glacier, although in Glacier 

 County a definite estimate for 1920 was not secured. Increased losses 

 ■were sustained in Hill and Liberty counties and several counties in 

 the eastern part of the State, namely, Dawson, Fallon, Prairie, and 

 Yellowstone, where large areas of corn and small grains were destroyed. 

 In 1922 only a very small part of the area formerly infested suffered 

 any damage and even in the two counties so affected. Hill and Liberty, 

 the losses were very small when compared with those sustained the 

 two preceding years. 



The great decrease in the destructiveness of the pale western cut- 

 worm in 1922 is thought to have been due more than anything else 

 to the heavy snowstorm which swept over most of the infested terri- 

 tory in northern Montana during the first part of September, 1921. 

 The parent moths were thereby destroyed or at least prevented from 

 depositing their eggs. Other reasons which may in part account for 

 the decreases in both 1921 and 1922 are better moisture conditions 

 during May and June than for several seasons past, greater preva 

 lence of the natural enemies of the cutworms, and early irrigation of 

 fields known to be infested. Thus the substantial reduction in Teton 

 County in 1921 is believed to have been due to irrigation. Several 

 fields on the Greenfield Bench whicli came under our observation 

 showed heavA^ manifestations just prior to the time water was turned 

 on them. Later reports showed these fields to have produced good 



