MONTANA INSECT PESTS, 1949 AND 1950 15 



ARMY CUTWORMS (Chorizagrotis auxiliaris) 



These destructive Lepidopterous larvae were not reported or 

 observed in 1949. In the spring of 1950 a moderate to severe out- 

 break of army cutworms occurred in Big Horn, Yellowstone, Car- 

 bon, Stillwater, Fergus, and Gallatin counties. Less severe, more 

 localized infestations probably occurred in areas adjacent to the 

 larger infestations. The greatest damage from this outbreak oc- 

 curred in April, primarily on fall planted winter wheat and alfalfa. 

 In the more severely infested areas, high populations of army cut- 

 worms were evident in range land adjacent to cultivated areas as 

 well as in the cultivated areas. Comparatively cool, damp weather 

 occurred in May and persisted throughout the balance of the spring. 

 Very little damage occurred after the onset of this cool, damp 

 M^eather, though the worms could still be found in the fields and 

 apparently were primarily feeding on weeds. A few army-like 

 migrations were observed, but these were not numerous. Excel- 

 lent control was obtained by the application of sodium fluosilicate 

 bran sawdust wet grasshopper bait. Good control was obtained 

 through the use of two pounds of toxaphene per acre as a spray 

 v/henever sufficient foliage was present to carry the toxicant. 



PALE WESTERN CUTWORMS (Agrotis orthogonia) 



No infestations of pale western cutworms were reported or 

 observed in 1949. In 1950 approximately 50 square miles of the 

 Kenilworth area in north central Chouteau County were severely 

 infested. This infestation persisted well into the early summer 

 season causing damage to the crops present and to the later plant- 

 ings. Nearly all crops in this area had to be planted late, some 

 for a second and third time. Several attempts to combat this out- 

 break with soil and seed treatments of benzene hexachloride were 

 reportedly imsuccessful. 



Serious damage to sugar beets by pale western cutworms oc- 

 curred in the Bitterroot Valley. In some fields the damage was 

 severe enough to cause as high as 50% loss of the beets in the 

 field. 



WIREWORMS (Elateridae Family) 



Infestations of wireworms have occurred in practically all 

 areas of the state during the past two years. Damage has been 

 particularly noted in dry land small cereals. The gamma isomer 

 of benzene hexachloride used as seed or soil treatment has pro- 

 vided good control. 



BLISTER BEETLES (Meloidae Family) 



Blister beetles caused considerable damage to sugar beets in 

 Custer County in 1949 and in Custer and Richland counties again 

 in 1950. Damage also occurred to alfalfa seed fields during both 

 3'-ears, particularly in the southeastern part of the state. Damage 



