MONTANA INSECT PESTS, 1951-1952 9 



WESTERN WHEAT APHID (Brachycolus tritici) 



In 1951 the western wheat aphid was reported only in southern 

 Broadwater County. Control measures were attempted by the 

 aerial application of one pound of parathion per acre. These meas- 

 ures were unsuccessful. The leaf sheaths of the wheat plants were 

 curled by the time the insecticide was applied. This provided pro- 

 tection for the aphids which were present inside of the sheath. 

 Most of the farmers worked their summer fallow so as to keep it 

 free from volunteer wheat, barley, and grasses. This practice pre- 

 vented over-wintering aphid colonies from establishing them- 

 selves in the fields and resulted in only spotted light infestations 

 in this area in 1952. 



Other spotted infestations were reported in 1952 in south- 

 western Choteau County and eastern Richland County. 



ENGLISH GRAIN APHID (Macrosiphum granarium) 



Late June and early July of 1951 were relatively cool and wet 

 in western Montana. By early July, English grain aphid popula- 

 tions had built up to alarming numbers in Ravalli, Missoula, 

 Sanders, Lake, and Flathead counties. Heavy flights occurred 

 generally throughout this area in mid-July, and specimens were 

 picked up by aircraft as high as 8,000 feet altitude. Some controls 

 were attempted using aircraft application, applying Yi pound of 

 parathion and one gallon of oil per acre. For the most part these 

 control measures were successful but tended to be somewhat er- 

 ratic. In the latter part of July the weather in western Montana 

 turned hot and dry allowing ^predators, principally syrphid fly 

 larvae, to rapidly reduce grain aphid populations. In mid-August 

 the weather turned damp and cool in an area involving parts of 

 Glacier, Toole, Pondera, and Teton counties. By the first of Sep- 

 tember, alarming populations of English grain aphids were present 

 in many of the grain fields, and some shriveling of kernels was 

 already evident in the ripening grain. Airplane spraying was im- 

 mediately initiated applying 3/8 of a pound of parathion in two 

 gallons of diesel oil per acre. The resulting control was excellent. 



In 1952 alarming numbers of English grain aphids appeared 

 in Daniels, Sheridan, and northern Valley counties following a 

 cool wet period in late July. Early August turned hot and dry re- 

 sulting in the aphid population rapidly falling below the eco- 

 nomic level principally due to the activities of ladybird beetles. 



WHEAT STEM SAWFLY (Cephus ductus) 



The 1951 wheat stem sawfly survey indicated that severe in- 

 festations occurred in Teton, Pondera, Glacier, Toole, Lincoln, 

 Chouteau, Cascade, and Daniels counties, with lesser infestations 



