4 MONTANA EXPERIMENT STATION BULLETIN 442 



Farmers operating small units which would not justify the ex- 

 tensive purchase of equipment can cooperate with their neighbors 

 and purchase the machinery necessary to carry on effective insect 

 control work. 



Farmers and ranchers should consider that insect control is 

 as much a farm practice as cultivation, plant and livestock breed- 

 ing, and many other operations that are necessary if their unit is 

 to be productive. 



MAJOR INSECT CONTROL PROBLEMS 



GRASSHOPPER CONTROL, 1945-46 



The grasshopper infestation in Montana has been increasing 

 each year since 1942, when the State experienced the lightest in- 

 festation in almost 10 years. 



During the period from 1938 to 1942 the dominant species in 

 heavily infested areas of the State was, almost without exception, 

 Melanoplus mexicanus. This was a result of the tremendous migra- 

 tion of this species into the eastern part of the State during the fall 

 of 1938, added to the heavy population already present. The carry- 

 over and continued westward migration of this grasshopper made 

 it the most important species for almost seven years. 



The present "build-up" is characterized by a gradual decrease 

 of M. mexicanus, and an increase of Melanoplus bivittatus, M. 

 jemur-mhrum,, and M. differentialis. The most noticeable increase 

 of these species of grasshoppers is in the eastern part of the State, 

 especially in the lower Yellowstone Valley, where they have re- 

 placed M. mexicanus as the dominant species. 



The presence of M. differentialis is comparatively new in the 

 State. Differential grasshoppers were first found in Dawson County 

 in eastern Montana during the fall of 1932. It was believed that 

 they flew in from South Dakota late in the fall." Their spread, since 

 that time, has generally been in a southerly and westerly direction, 

 almost to the Wyoming line in Big Horn County. In many areas in 

 the eastern part of the State they have become the dominant 

 species. 



During the last few years the standard bran bait has not been 

 effective in controlling grasshoppers infesting alfalfa fields, field 

 margins, and road right of ways where the vegetation remains 

 green and succulent during most of the summer. As a result of in- 

 adequate control methods, much grasshopper damage has occurred, 

 especially in areas where seed alfalfa is grown. Experimental work 

 has been carried on in an effort to find insecticides which will give 



»Mont. Agr. Exp. Sta. Bull. 269, p. 10. 



