22 MONTANA EXPERIMENT STATION BULLETIN 36G 



OTHER IMPORTANT INSECTS OF THE YEARS 1937-1938 



PALE WESTERN CUTWORM 



(Agrotis orthogonia Morr.) 



It has been pointed out in previous reports that the abun- 

 dance of this pest is directly correlated with the rainfall in May 

 and June of the preceding year. Annually an examination of 

 the weather records for the State is made and the possibility of 

 outbreaks of this pest is ascertained. With this information avail- 

 able it is possible to alter farming practices so as to practically 

 eliminate injury the following year. 



The pale western cutworm lays its eggs, approximately be- 

 tween August 15th and September 15th, in worked soil which is 

 without a crust. Therefore, a field which is to be planted to 

 wheat the following season should not be worked between these 

 two dates. Further, Seamans 1 has shown that there is a possibility 

 of eliminating these insects in the spring from infested fields. 

 He has shown that the newly hatched larvae feed on the sur- 

 face for a period in the spring before going into the ground. 

 They are dependent on green food. Further, they may live for 

 some time without food provided they have not eaten, but once 

 they have taken food they starve quickly when it is not avail- 

 able to them. On the basis of these observations he suggests that 

 fields, in which infestations are expected to appear, be allowed 

 to green slightly in the spring so that the newly hatched larvae 

 may have a chance to feed. The fields then should be cultivated 

 in such a way that no growing plants appear above the surface 

 of the soil for at least 5 days. Seeding may then follow and 

 there is a high probability that most of the little larvae will 

 have starved before green vegetation again appears. 



Fortunately the weather experienced during the spring of 

 1938 indicates that injury from pale western cutworm is not 

 likely to occur anywhere in Montana in 1939. 



ARMY WORM 



(Cirphis unipunctata Haw.) 



True army worms have been taken in Montana at Hardin, 

 Havre, Hamilton, Waterloo, Malta, Miles City, Bozeman, Three 



'Seamans, H. L., Scientific Agriculture, Vol. 17, No. 10: 612-615, June, 

 1937. 



