Montana State Library 



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MONTANA INSECT PESTS 1939 AND 1940 

 Twenty-Eighth Report of the State Entomologist 



Harlow B. Mills 



INTRODUCTION 



The years 1939 and 1940 were characterized, as have been all 

 in the decade just past, by intense grasshopper infestations in a 

 large part of the State. These pests again were by far the domin- 

 ant injurious insects, and their numbers were tremendous. 



During the past three years, flights of the lesser migratory 

 locust (Melanoplus mexicanus Sauss.) have been one of the out- 

 standing biological phenomena of this region. This species, which 

 is known to have migratory tendencies, has been comparatively 

 quiescent in the State for many years, and the migrations which 

 occurred were of small proportions and for short distances. As was 

 reported in the Twenty-Seventh Report of the State Entomologist 1 

 the native populations of all species of grasshoppers in the State 

 were at a low ebb in 1938. On the first day of July of that year, im- 

 mense numbers of the lesser migratory locust invaded the State 

 from the southeast, traveling as far to the northwest as Blaine, 

 Fergus, Petroleum, Rosebud, and Treasure counties. Large num- 

 bers of eggs were laid in the east-central area, involving Phillips, 

 Valley, Daniels, Sheridan, Roosevelt, Richland, Dawson, Wibaux, 

 Fallon, Prairie, Custer, Rosebud, Treasure, Garfield, and Petroleum 

 counties. This area was delimited by the survey of the autumn of 

 1938. and preparations were made to combat the hatching 'hoppers 

 in the spring of 1939. The control operations were complicated by 

 the deposition of large numbers of eggs in idle and reverted lands, 

 and in depleted range which was being invaded by such annual 

 weeds as Russian thistle and tumbling mustard. 



To meet this new and unusual condition, the United States De- 

 partment of Agriculture, through the Bureau of Entomology and 

 Plant Quarantine, instituted a new program, furnishing bait, mixing, 

 transportation, and crews to poison infested, reverted, and range 

 land from which migrations might originate. This was in addition 

 to the usual cropland program in which bait materials were furn- 



~ 'Montana Experiment Station Bulletin 366, 1939, pp. 12-16. (Out of 

 print. Available only in libraries.) 



