MONTANA INSECT PESTS, 1955-1956 7 



It has become apparent during the last year that control of these 

 pests by chemicals is a definite possibility. Heretofore, baiting was 

 the only acceptable method of control because of the extremely resis- 

 tive nature of the Mormon cricket toward poison sprays. During 

 grasshopper control work in 1955 it was noted that crickets in the 

 same areas were also controlled. Consequently, cricket control using 

 chemicals alone was tried during 1956. On large areas treated by 

 aircraft with one ounce of dieldrin per acre the kill appeared satis- 

 factory. 



ARiMY CUTWORMS (Chorizagrotis auxiliaris) 



Army cutworm damage was comparatively light during both 1955 

 and 1956. The northern tier of counties experienced local light-to- 

 medium infestations during the former year. As a rule, these infesta- 

 tions were a month or more later than usual. During 1956 only scat- 

 tered late infestations were observed. These occurred in Rosebud, 

 Liberty, and Chouteau counties. The newly planted lawns of a 

 housing development in Glendive were ruined by this pest. One of 

 the newer chlorinated hydrocarbon insecticides known as endrin has 

 worked very well against this cutworm at rates of .1 to .2 pound per 

 acre. 



BLISTER BEETLES (Coleoptera: Meloidae) 



Populations of these insects have been higher during the past 

 biennium. Lytta cyanipennis, L. nuttali, and L. sphaericollis were the 

 most damaging species. Alfalfa, clover, beans, caragana, and other 

 legumes were attacked. Infestations were scattered in many places 

 east of the mountains. 



FLEA BEETLES (Coleoptera: Chrysomelidae) 



Damage by flea beetles has been scattered but severe in spots. 

 In 1955 there were apparently more of these beetles than in 1956. 

 Alfalfa and beans were the main crops attacked by Systena blanda 

 and Disonycha triangularis. The Western flea beetle, Phyllotreta pusilla, 

 caused severe damage to mustard in Pondera County. 



WIREWORMS AND FALSE WIREWORMS 

 (Coleoptera: Elateridae & Tenebrionidae) 



During the fall of 1954 very large field populations of adult false 

 wireworms were noted in the Triangle Area and in spots along the 

 northern tier of counties. In the spring of 1955 there had apparently 

 been a large survival of larvae since extensive infestations developed 

 over the northern part of the state. Where treated seed was planted 

 at the ordinary depth, not too much damage resulted. However, where 



