MONTANA INSECT PESTS 1945-1946 5 



satisfactory control of grasshoppers in alfalfa fields. A number of 

 new insecticides, including 1068, Hercules 3956, benzine hexachlor- 

 ide, and P. C. H. have been tried. Some of these have given very 

 promising results and will be recommended for use in alfalfa fields 

 to supplement present control methods. 



1945 SEASON 



The grasshopper adult and egg surveys made in the fall of 

 1944 indicated that a severe outbreak was likely to occur in the 

 eastern part of the State, especially along the Yellowstone valley. 

 Light to threatening populations were expected in Big Horn, Yel- 

 lowstone, Treasure, and Rosebud counties; in the northeastern 

 comer as far west as Blaine County; in Hill, Liberty, Toole, Gla- 

 cier, Pondera, Teton, Cascade, and Chouteau in the north central 

 area; and in Ravalli, Missoula, Lake, Sanders, and Flathead coun- 

 ties in the western part of the State. 



Cold weather in the spring delayed the egg hatch considerably, 

 and it was late in June before the 'hoppers began to appear in large 

 numbers. Hatching in some areas continued until late summer. 



Heavy weed growth along borrow pits, fence rows, and on idle 

 lands furnished succulent feed during most of the season. Because 

 of this, grasshopper movements into cultivated areas were delayed 

 and the spreading of bait materially lessened. 



The most severe infestation developed in the lower Yellow- 

 stone valley in Custer, Prairie, Dawson, and Richland counties and 

 in Hill, Chouteau, Pondera, Cascade, and Teton counties, in the Tri- 

 angle area. The dominant species in the Yellowstone valley was 

 M. dijferentialis, with M. hivittatus second and M. mexicanus third. 

 M. mexicanus was the dominant species in the Triangle area with 

 M. hivittatus second in importance. Adult grasshoppers were first 

 observed July 15, and egg laying started about August 15. 



Nymphal population in some areas was reduced by cold weath- 

 er. Sarcophagid flies were instrumental in reducing M. differentialis 

 population in Custer county. In the lower Yellowstone valley, M. 

 dijferentialis and M. hivittatus were affected by fungus with some 

 reduction in numbers resulting. Destruction of egg pods by blister 

 beetle and carabid larvae was evident in the north central part of 

 the State. 



In spite of the fact that there was a shortage of labor and equip- 

 ment, the 1945 grasshopper control campaign was quite successful. 

 Early season kills, especially in alfalfa, were not satisfactory, but 

 late season baiting in all habitats was highly successful. Federally 

 financed control work was carried on in Dawson, Prairie, Richland, 

 Custer, and Chouteau counties. Crews paid by the Bureau of En- 

 tomology and Plant Quarantine operated federally-owned trucks 



