S MONTANA EXPERIMENT STATION Bui. 133 



CURRENT ENTOMOLOGICAL PROBLEMS 



Some of the outstanding entomological problems of the present 

 time are the following: 



PALE WESTERN CUT^VOR^[ 



For several years we have been giving attention to cutworms 

 in garden and tield crops in Montana and gradually information of 

 considerable value is being brought together. It is evident that 

 there is a considerable variety of very destructive cutworms in the 

 state, though in any one year the trouble is caused mainly by some 

 one or another single species. The species which is best known 

 in Montana is undoubtedly the army cutworm {Choriza§rotis aux- 

 iliaris Grote) which at times has caused extensive damage to fall 

 wheat, but during the past few years there has appeared another 

 which is quite as serious. This is the pale western cutworm 

 {PoTosa^votis orfJio^onia ^Morr.") which has been mentioned in 

 previous reports, but which we are, year by year, recognizing as 

 more serious than we had suspected. Without much doubt over 

 a million dollars' worth of grain was destro^-ed in Montana in 1919. 

 Similar extensive damage occurred in Canada, just north of Montana, 

 in the same year. There appear to be four reasons why this is an 

 unusually injurious cutworm. (1) It has a long period of larval 

 feeding extending from the middle of April for upward of two 

 months. In this it contrasts strongly with the army cutworm which, 

 wlien abundant, attracts attention in April and is all through feeding 

 by May 10, or about a month in all. (2) Its damage is done so late 

 in the season that it is too late to put in a crop of spring grain, as 

 can l)e done sometimes when the grain has been eaten off by the 

 army cutworm. (3) The pale western cutworm feeds under ground 

 and we know of no practical way to kill it. Poisoned bran mash 

 scattered thinly over the surface, so effective in controlling the 

 army cutworm, does not atfect this species. (4") It is not heavily 

 attacked by parasites and continues year after year, gradually becom- 

 ing more abundant and destructive. This cutworm has already 

 become a serious problem in Montana and is receiving careful atten- 

 tion from this office. Under our Experiment Station research funds 

 we are studying its habits and control. Excellent progress has been 

 made and we have much information of value but no satisfactory 

 rcmedv has vet been worked out. 



