16 MONTAJNTA EXPERIMKNT STATION BULLETIN 442 



HESSIAN FLY {Phytophaga destructor). — The Hessian fly 

 continued to be a severe spring wheat pest in parts of eastern Mon- 

 tana during 1945, when weather conditions again favored its in- 

 crease and depredations. Figure 2 shows the area most seriously in- 

 fested. Damage in some fields amounted to total loss of the crop 

 and losses of 50 per cent or more were common. 



Because of the serious nature of the infestation, some cultural 

 controls were attempted by the farmer. Attempts were also made 

 by this office to check on reported resistance of certain wheat 

 varieties to Hessian fly attack, but data collected were not conclu- 

 sive. Plans were made to test these varieties experimentally in 

 1946, but the 1946 infestation failed to materialize, possibly because 

 of the cool, dry spring. No infestations of economic importance 

 were found during the entire season, and, after two years of ob- 

 vious damage to wheat crops, the Hessian fly has apparently re- 

 verted to its position as a pest of relatively little importance to 

 Montana. 



FALSE CHINCH BUG (Nysius ericae) . — This insect is com- 

 mon and sometimes abundant in Montana, but its injury to crops is 

 usually not sufficiently intense to be noticed. However, in the sum- 

 mer of 1945 it migrated in large numbers into a mustard field north 

 of Valier in Pondera County where it attacked the plants near the 

 ground line, completely destroying most of an 80 acre field. Control 

 measures against this pest have not been developed. 



ARMY CUTWORM (Chorizagrotis auxiliaris) . — These early sea- 

 son pests were in evidence in Montana during both of the past two 

 years. Their feeding on winter wheat was conspicuous, and con- 

 siderable damage was done. 



During the spring of 1945 an area in the central part of the 

 State comprising parts or all of Chouteau, Judith Basin, Fergus, 

 Petroleum, Wheatland, Golden Valley, Musselshell. Treasure, Yel- 

 lowstone, Stillwater, Carbon, and Big Horn counties were infested. 

 It was estimated that more than 300,000 acres were affected and 

 approximatey 1,000 acres were completely destroyed. 



In 1946 the infestation appeared in the southeast corner of the 

 State, involving the Powder River-Fallon county area. 



The army cutworm readily takes the sodium fluosilicate grass- 

 hopper bait, and control has been successful with this material. A 

 considerable amount of bait was used in stopping these pests in 

 both years. 



