MONTANA INSECT PESTS, 1951-1952 13 



seed clover fields of western Montana during the biennium. In 

 addition, an infestation was reported in a seed clover field in 

 Yellowstone County in 1952. This insect seems to occur in eco- 

 nomic numbers in seed clover fields frequently enough to justify 

 a preventative benzene hexachloride spray program. 



LESSER CLOVER LEAF WEEVIL (Hypera nigrirostris) 

 During the biennium, the lesser clover leaf weevil continued 

 to be present in economic numbers in the seed clover fields of 

 western Montana. 



In 1952 this weevil was found to be present in some irrigated 

 pastures in Big Horn and Yellowstone counties where it was caus- 

 ing severe defoliation to the clover and greatly reducing the food 

 value of the infested pastures. Control measures under these par- 

 ticular circumstances have not as yet been worked out. 



SMALL MILKWEED BUG (Lijgaeus kahnii) 

 The small milkweed bug has been observed to be present in 

 insignificant numbers in many southeastern Montana alfalfa 

 fields. A severe infestation of this insect occurred in early June 

 of 1952 in an alfalfa field in Treasure County. They were report- 

 ed to be killing the alfalfa plants. 



POTATOES 



COLORADO POTATO BEETLE (Leptinotarsa decemlineata) 

 Scattered moderate to heavy infestations of Colorado potato 

 beetles occurred in most of the potato growing areas of the state 

 during the biennium. Many of the potato growers are somewhat 

 reluctant to carry out an insecticidal control program; conse- 

 quently, in most cases only the more severe infestations were 

 treated. 



Aerial spraying for Colorado potato beetle control was tested 

 on three fields in the Gallatin Valley in 1952. The spraying was 

 accomplished with an Aeronca Champion spray plane applying 

 one pound of DDT per acre with diesel fuel as a solvent at a total 

 volume of one gallon per acre. The fields had moderate to heavy 

 infestations of potato beetles and this spray application eliminat- 

 ed the infestation. Some foliage burning was noted; however, this 

 burning was not extensive enough to affect yields. The potato 

 plants in the test fields were somewhat smaller than average for 

 late summer and the rows were not closed in as would normally 

 be the case. A total volume of one gallon per acre appeared to be 

 adequate for Colorado potato beetle control on these smaller 

 potato plants. 



POTATO PSYLLID (Paratrioza cockerelli) 

 A severe infestation of potato psyllid was observed in Dawson 



