34 MONTANA EXPERIMENT STATION BULLETIN 294 



Sugar-beet Maggots 



A maggot of an uiidetermiiied species caused severe damage in 

 a number of beet fields in southern Montana by cutting off the root 

 system (1934). 

 The Beet Welnvorm {Loxostege sticticalis L.) 



This insect was of slight, if any importance, in 1933 and 1934. 

 Many moths emerged in ]\Iay, 1933. Init the number of larvae which 

 developed was extremely small. This was a remarkable decline from 

 the very extensive outbreak of 1932. 

 The Colorado Potato Beetle (Leptinotarsa deci)nlineata Say) 



This destructive insect was far more abundant over the state in 

 1934 than for several seasons. 



VEGETABLE AND TEUCK CROPS 



Cabbage Maggot {Phoibia brassicae Bouche) 



In spite of a heavy emergence of flies and the deposition of great 

 numbers of eggs on young cabbage plants — especially in the Bitter 

 Root Valley — this insect caused an insignificant amount of damage 

 in 1934. For some unknown reason the eggs failed to hatch. The 

 cabbage butterfly {Pieris rapae L.)and the cabbage aphis {Brevi- 

 coryne brassicae L.) were unusually abundant and destructive. 



FRUIT INSECTS 



The Black Cherry Aphis {llyzus cerasi Fab.) 



There are now 49,466 cherry trees in the Flathead Lake region. 

 The great proportion of these are young sweet cherry trees which have 

 been set out during the past three or four years. One of the most in- 

 jurious pests of young cherries is the black cherry aphis. It with- 

 draws the plant sap and curls the leaves, thus devitalizing the trees, 

 and distorts the terminal growth. (See figure 7.) 



The main causes of failure to control this insect in the past have 

 been poor spraying — due largely to lack of })roper equipment — and 

 poor timing of the sprays that were put on. It was demonstrated in 

 1934 that from 9-3 to 98 per cent control could be obtained by two 

 sprays. The first was applied shortly after the first young aphids 

 had hatched from the overwintering eggs and were resting on the 

 opening buds (March 24). The second was applied April 12 to catch 

 the late hatch of aphis. Thus the majority of the plant lice were 

 killed before the leaves were out. After tlie leaves have begun to 

 curl spraying is ineffeetiA'e. 



