18 
BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
grasses. The infestation in crops, other than corn, is especially likely 
to occur (1) when corn is growing near by, (2) when the infested 
crop remnants and weeds from previous crops on the same or ad- 
jacent areas have not been destroyed, and (3) when susceptible weeds 
are growing in the field or in its immediate vicinity. Many weeds 
are included as hosts, thus serving to complicate the control of the 
Fig. 4. — Smartweed (Polygonum sp. ), a favorite weed host of the European corn 
borer 
pest and aiding in its multiplication and dispersion. Occasionally 
in certain fields some of these weeds, notably cocklebur (Xanthium 
spp.. fig. 3). barnyard grass (Echinoehloa crus-galli (L.^ Beauv.), 
and smartweed (Polygonum spp., fig. 4.), appear to be preferred as 
hosts rather than corn. 
