T\vi;\'iv i-onrni in-:i'()irr of state entomoix)GIST 7 



by the Montana Experiment Station liave sliown that dry conditions 

 during' M;iy, Jnne, and Jnly hi-infj about the increase of tlie cutworm 

 \vliich results in ci'oi) (hinia^'e the followinor year. Two dry years 

 in succession an' esfxH-ially serious with respect to pale western eut- 



MONYANA 





Figure 1. — The 1932 outbreak of the Pale Westeru Cutworm. About 

 ] 40,000 acres of crop was damaged. 



worm abundance. Once the pest becomes bad, more than one j^ear of 

 normal weather is required before the cutworm numbers are reduced. 



Su])normal moisture conditions during the critical periods in 

 1930 and 1931 were responsible for the 1932 outbreak, which was 

 predicted in advance on the basis of precipitation records. The 

 normal rainfall during the 1932 season undoubtedly restricted develop- 

 ment of the cutworms, nevertheless some carry-over into 1933 is 

 expected in the districts which are infested. This prediction is based 

 upon observation of fair flights of the mollis in those areas during 

 the first week in September and upon the history of the similar 

 carry-over effect in 1921. Only those districts which experienced 

 trouble last spring are expected to harbor infestations again in 1933. 



The general showers during the latter part of August this season 

 came at a very desirable time since crusts were formed over fallow 

 fields which, if left unbroken, made the surface unattractive for 

 egg-laying. Stubble fields which were disturbed by harvesting 



