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BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
serve to attract attention to infested plants at an early stage of the 
injury. Later in the season, or as the result of heavy rains, much of 
the frass becomes separated from the plant and falls to the ground. 
The tunneling of one or two larvae in a stalk does not always 
cause appreciable damage; but where, as frequently occurs, several 
or many borers are tunneling and feeding within the same stalk, it 
Fig. 9. — Longitudinal section of ear of sweet com damaged 
by European corn borer, showing entrance of larva, the 
stem, and cob 
becomes reduced to a mere shell filled with frass and particles of 
decayed and putrefied plant matter. Naturally the stalk is greatly 
weakened by this type of injury, and eventually it collapses and 
breaks over at one or more places. (Fig. 10.) Such breakage may 
also occur during wind or rain storms as a result of the tunneling of 
even one or two borers. 
