MONTANA INSECT PESTS, 1955-1956 11 



CORN EARWORM (Heliothis arniigera) 



This pest has been present only in moderate numbers through the 

 last 2 years. It is, however, a nuisance and preventative measures 

 have to be taken wherever sweet corn is raised for market. 



Alfalfa and Clover Insects 



ALFALFA WEEVIL (Hypera postica) 



This insect remains the number one pest of alfalfa in the state 

 and each year infests new areas. Practically all of the counties east 

 of the mountains now have economic infestations. Approximately 

 300,000 acres of alfalfa are treated each year at a cost of about $400,000. 

 Increase in yield where treatment is practiced produces an average 

 of 1 ton per acre more forage and is valued at $4,500,000 for the 

 300,000 acres for a net saving of over $4,000,000. Each year a series 

 of meetings is held in newly invaded territory to acquaint farmers 

 with the proper control methods. 



LYGUS BUGS (Lygus sp.) 



In areas where alfalfa seed production is important, lygus bugs 

 invariably affect yields. A lot of time and effort has been put into 

 informing producers and spray operators of the correct control prac- 

 tices for this pest. Unfortunately an incorrectly conceived spray pro- 

 gram can do more harm than good since pollinators may be eliminated 

 and reduced seed set result. The eastern part of the state, from 

 Roosevelt County south to Wyoming and west to Yellowstone County, 

 is the area most severely damaged by lygus bugs. 



CLOVER APHID (Anuraphis bakeri) 



1956 was the first time that this pest had been present in economic 

 numbers for a number of years. Because of the sporadic nature of 

 infestations, no really reliable methods of control have been worked 

 out. Carbon, Yellowstone, Rosebud, and Big Horn counties experienced 

 difficulty with this insect where clover was grown for seed. 



CLOVER SEED CHALCID (Bruchophagus gibbus) 



This pest was known to be harmful only in Rosebud County in 

 1955. 



Potato Insects 



COLORADO POTATO BEETLE (Leptinotarsa deccmlineata) 



No infestations were reported or observed during 1955. Scattered 

 infestations occurred on potatoes in the western counties in 1956. 



