20 MONTANA EXPERIMENT STATION BULLETIN 474 



red where control measures were not administered. Four-tenths 

 to one-half pound of gamma isomer of benzene hexachloride per 

 acre, properly applied, has satisfactorily controlled this insect. 



LESSER CLOVER HEAD WEEVIL (Phytonomus nigrirostris) 



The lesser clover head weevil has been prevalent in western 

 Montana during the past two years, and is a contributor to the 

 insect hazard involved in the raising of clover seed. Control has 

 been accomplished by a pre-bloom clipping in June, allowing the 

 second growth to go to seed. 



PEA APHID (See Pea Insects) 

 POTATOES 



TUBER MAGGOT (Eumerus spj 



These fly larvae were found in the Missoula area in 1950 as 

 a secondary infestation in potatoes. The tubers had previously 

 been tunneled by wireworms. 



PSYLLID (Paratrioza cockerelli) 



COLORADO POTATO BEETLE (Leptinotarsa decemlineata) 



These insect pests have on past occasions been highly destruc- 

 tive to potatoes in Montana. They have not been a serious problem 

 in the last two years. This is probably because potato growers 

 have used DDT, which is very effective against these two potato 

 insect pests. 



WIREWORMS (See General Feeders) 



SUGAR BEETS 



SUGAR BEET ROOT MAGGOT (Tetanops aldrichi) 



During the past two years, the sugar beet root maggot has 

 been an economic problem in Yellowstone County, and the Bitter- 

 root Valley. Control measures were applied in 1950 on about 50% 

 of the sugar beets in the Bitterroot Valley with satisfactory results. 

 The pre-planting soil application of one pound of gamma isomer 

 of benzene hexachloride mixed with the fertilizer (when sugar 

 beet root aphids are a factor) or four pounds of chlordane (when 

 sugar beet root aphids are not a factor) has given excellent control. 



SUGAR BEET ROOT APHID (Pemphigus hetae) 



The sugar beet root aphid, a sucking insect on the beet root, 

 is widely distributed throughout the sugar beet growing areas of 

 western Montana. Infestations in 1949 were high, resulting in 

 considerable damage. Populations were extremely low in 1950. 

 The recommended pre-planting soil application of one pound of 

 gamma isomer of benzene hexachloride mixed with fertilizer has 

 apparently provided satisfactory control. 



