MONTANA INSECT PESTS, 1947 AND 1948 11 



grains in this area. Another cutworm species was reported to have 

 damaged the terminal buds of sour cheery plantings in the Bitter- 

 root Valley. 



PALE WESTERN CUTWORMS (Agrotis orthogonia) 



Pale western cutworm damage was observed in the vicinity 

 of Great Falls and Havre during 1947 and 1948. The infestations 

 were small and occurred in localized areas. Heavy flights of pale 

 western cutworm moths were observed in the north-central part 

 of the state during the fall of 1948. 



The practice of trash fallowing in the above area may produce 

 conditions more favorable for egg deposition by the adult moths. 

 Since the moths select uncrusted soil in which to lay their eggs, 

 the action of the wind on the trash present in this type of fallow 

 may prevent the formation of a crust adjacent to the exposed 

 stems, thus increasing the areas within a field which are suitable 

 for egg laying. This may be another instance where cultural prac-' 

 tices are at least in part responsible for producing conditions which 

 are favorable for the spread of an insect during the outbreak 

 years. Further investigations are necessary to determine the exact 

 effect of these practices on the relationship which exists between 

 this insect and the condition of the fallow. 



HESSIAN FLY (Phytophaga destructor) 



The Hessian fly occurs in the northern and eastern parts of 

 Montana. In 1924 and again in 1944 this insect caused considerable 

 damage to wheat in these areas. During the last two years, hessian 

 flies have been observed in small numbers but sufficient popula- 

 tions have not developed to make this pest of any great economic 

 importance. 



WHEAT STEM MAGGOT 



During the 1948 season, the stem maggot has been observed 

 occurring in large numbers over the state. It has been especially 

 noticeable in Big Horn, Yellowstone, and Cascade counties. While 

 it has caused some damage to wheat, it has been more destructive 

 to crested wheat grass in these counties. To date actual determina- 

 tion of the species involved has not been made. 



CORN 



CORN EAR WORM (Heliothis armigera) 

 No report of the corn ear worm having caused damage in 1947 

 was received. In 1948 a field of sweet corn near Park City was 

 observed to have a corn ear worm infestation. Approximately 

 30-40 percent of the ears were damaged. No other infestations were 

 reported or observed in the state. 



