MONTANA INSECT PESTS. 1955-1956 9 



east had reported high populations by the middle of June but the 

 first infested fields were reported in Montana about the first of July. 

 By the 10th of that month barley throughout the state was infested. 

 Since there were no previous records of this insect's occurrence in 

 the state, a period of intensive study was necessary before control 

 recommendations could be made. As far as we were able to ascer- 

 tain, barley was the only crop attacked. Corn, wheat, oats, and other 

 cereals were not infested even though grown in mixed stands with 

 barley. 



Many of the fields inspected had populations of these bluish- 

 green plant lice averaging several hundred per plant. In these fields 

 the late-planted barley turned yellow and was stunted. In fields 

 where the barley had started to head before being infested the damage 

 was much harder to see and many fields showed no decreased yields 

 at harvest time. 



Insect predators in the form of syrphid flies and lady bird beetles 

 completely eliminated the aphids from some fields in a matter of a 

 few days. In other fields, malathion was applied at 12 ounces per 

 acre with very good results. 



There were no cases of infestation by this insect in 1956. 



WHEAT CURL MITE (Aceria tulipae) 



This pest which was responsible for such a severe infestation of 

 wheat streak mosaic in 1954 was found only in noneconomic, scattered 

 infestations in 1955. It appeared to be absent in the state in 1956. 



ENGLISH GRAIN APHID (Macrosiphum granarium) 



This summer pest of wheat occurred about the same time as the 

 corn leaf aphid in 1955 in the eastern and northern tier of counties. 

 No damaging infestations were reported, but because of the concur- 

 rently large populations of both of these aphids a good deal of con- 

 fusion existed regarding the status of the English grain aphid until 

 the situation was cleared up. No infestations were reported in 1956. 



WHEAT JOINTWORM (Harmolita tritici) 



Indications are that the wheat jointworm is building up, especially 

 in the central part of the state. Damage by this pest was reported 

 in Stillwater and Carbon counties in 1955 and probably occurred over 

 a wider area but was not reported since mild infestations are not 

 readily noticed by farmers. During 1956 some particularly heavily 

 infested fields were noticed in Sweet Grass County, which upon 

 evaluation proved to be between 80 and 100 percent infested. Under 

 these conditions the plants were stunted and most of them did not 



