10 FARMERS’ BULLETIN 640. 
the infested plants change to yellow and then brown, but the darker 
color and rank growth of leaf always precede this. 
In summer, in both spring and fall wheat, the effect of the fly is to 
cause the straw to break over before harvest. It is then said to be 
‘straw fallen.” 
Fra. 10.—Young wheat plant infested by the Hessian fly. (Author’s illustration.) 
IMMUNE OR DISTASTEFUL VARIETIES OF WHEATS. 
There is no such thing as “ fly-proof wheat.”” Most wheats will suf- 
fer when the plants are young, regardless of variety. In experimen- 
tal sowings a variety that seems to escape attack one year may suffer 
the next; and, while the insect may prefer certain varieties over others, 
this all comes to naught in years of serious ravages or where the sup- 
