3o6 Journal of Agricultural Research voi. xxn, no. 6 



major importance. During the last two years P. orthogonia has been re- 

 sponsible for losses in central Canada amounting to several million dollars. 



In Montana the pale western cutworm has been on the increase since 

 it was first noticed in 19 15 and is now the most destructive insect pest 

 with which the grain grower has to contend. In 19 15 at Conrad 80 acres 

 of wheat were destroyed and were reseeded to oats, which was also taken. 

 Flax was then seeded, but this also was so badly injured that the owner 

 plowed the field and summer fallowed it. This instance was typical of 

 scores of losses in the district now composed of the counties of Chouteau, 

 Teton, and Pondera. 



During the next two years, especially in 19 17, great losses were sus- 

 tained throughout the north central portion of the State, due to cut- 

 worms which worked entirely beneath the surface of the soil and which 

 were doubtless no other than Porosagrotis orthogonia. In 1919 the pale 

 western cutworm appeared in destructive numbers farther south and 

 caused severe losses in Park and Jefferson Counties as well as in the 

 previously infested area. A conservative estimate of the losses for the 

 year based on the reports of county agents, hundreds of questionnaires 

 returned by farmers, and the personal investigation of many fields in 

 different parts of the State, is at least 200,000 acres. In 1920 the injury 

 in Jefferson and Park Counties was more widely extended, and there was 

 a decided increase in the damage done in many of the districts previously 

 infested. The loss over the entire State for the year is placed at 250,000 

 acres, valued at $3,000,000. In the Willow Creek district in Jefferson 

 County a careful survey conducted in 1920 showed that 29 per cent of 

 the total seeded area had been destroyed by this cutworm, and a similar 

 survey in several of the northern counties showed a loss of 35 per cent of 

 the grain crops planted. 



To show perhaps a little more clearly what this cutworm has been 

 doing it may be stated that 100 fields personally inspected during the 

 summer showed a loss of 2,437 acres out of a total of 6,844 ^^ 1919, and 

 in 1920 a loss of 3,382 acres out of 6,844, or 35.7 per cent in 1919 and 

 49.4 per cent in 1920. Mr. George O. Sanford, manager of the Sun River 

 irrigation project, has stated to us that of the 15,300 acres seeded to crop 

 on the Greenfield Bench in 1920, 7,345 acres was a total loss and that 

 some damage was done to the remainder. Using the figures he has given 

 for the average yields on the undestroyed acreage — wheat 11.5 bushels, 

 oats 20.86 bushels, and flax 6.31 bushels — the average value of tlie prin- 

 cipal farm crops of that section was at least $15 per acre. Accordingly, 

 using that as a fair valuation per acre of the crops destroyed, the pale 

 western cutworm inflicted a loss of $110,175 in this one comparatively 

 small territory. Although these losses took place on irrigable land, no 

 water was available until after the first of June. Were it not that irri- 

 gation made it possible in some cases to reseed and grow a late crop on 

 part of the originally destroyed area, the loss would have been 55 per 

 cent instead of 48 per cent of the acreage in that district. 



