NINETEENTH REPORT OF STATE ENTOMOLOGIST 13 



crops. In a few instances, notably in Jefferson County, fields on wliicli 

 winter wheat was destroyed by this insect in the spring of 1921 were 

 reseeded to spring wheat with success, due mostly, it is believed, to 

 the good growing conditions which prevailed. On the other hand, 

 during the same year in Cascade County, one man is known to have 

 seeded 240 acres three times without getting a crop, which is a typi- 

 cal example of the extreme destructiveness of this species of cut- 

 worm under conditions most favorable to it. That dry weather is 

 the greatest contributing factor in outbreaks of this cutworm has 

 been conspicuously demonstrated. In 1921 in the drought areas losses 

 were maintained and in some instances increased over what they were 

 in 1920 but where better moisture conditions existed losses decreased. 



The season of 1922 saw a higher percentage of parasitism in the 

 pale western cutworm than had been known in the State before. At 

 the height of its destructiveness the lack of any parasitic enemies was 

 very conspicuous but last summer as high as 42 per cent of the worms 

 was destroyed by insect parasites. The mortality rate was increased 

 to such an extent by disease and predaceous enemies that there is little 

 possibility of this pest's causing material damage during the coming 

 year. 



The investigational work has not developed any direct method of 

 destroying the worms. The main feature bearing on control brought 

 out by Dr. W. C. Cook is that in some years early spring plowing 

 (before May 1st) will prove an effective means of preventing damage. 

 Briefly stated our control recommendations are based upon the fol- 

 lowing : 



1. As a general practice, summer fallowed ground, plowed early 

 and treated as recommended by the Montana Experiment Station, will 

 be least affected by the pale western cutworm. 



2. Good summer fallow which is not worked in any way between 

 July 15th and September 15th will have a better chance than that which 

 is worked during that time, due to the preference of the moths for 

 freshly worked or "mulchy" ground in which to deposit their eggs. 



3. In some years early spring plowing will prove as effective as 

 summer fallow. This method must have restrictions placed upon it 

 because it is believed that when the eggs fail to hatch in the fall, or, 

 if hatched, the young worms fail to make growth in the fall, spring 

 plowing before May 1st will destroy them. But when the eggs hatch 

 early and the worms are of fair size when thej^ go into hibernation, 



