142 BULLETIN 1476, U. S. DEPARTMENT OF AGRICULTURE 
the control efforts are directed principally against the corn plant 
and its residues, under present conditions. 
The value of corn and other plants for fodder is not materially 
lessened when infested by the corn borer, except under conditions of 
extreme infestation. The proper ensiling or shredding of such in- 
fested plants leads to the destruction of the borers contained 
therein. Feeding infested fodder direct to livestock is an effective 
method, providing all uneaten portions are collected and destroyed. 
The burning of infested material is, of course, a method of wide 
application, and although not a desirable agronomic practice in 
many respects, it is very effective when conducted in a thorough 
manner. In all methods of cutting cornstalks preparatory to their 
utilization or destruction, the stalks should be cut at or near the 
surface of the soil and as early in the season as possible, since there 
is a decided movement of the borers to the lower part of the stalk 
during the later part of the season. Based upon the results of plow- 
ing experiments to date, it appears that clean plowing is to be recom- 
mended for the destruction of cornstalks, corn stubble, and other 
infested material remaining in. the field, which it is impracticable 
to eliminate by burning or feeding. Late fall plowing in the two- 
generation area of New England has proved more effective than 
spring plowing, but in the middle West it appears from results of 
experiments to date that clean plowing at any season is effective. 
Relative to the selection of varieties as a cultural practice, none 
tested have shown any indication of possessing practical immunity to 
attack, but those varieties characterized by large stalks and ears 
have shown a greater resistance to severe injury by the corn borer 
than the varieties which have smaller stalks and ears. 
Experimental data and field observations have shown in general 
that in the single-generation areas field and sweet corn planted during 
April or early May have sustained the maximum infestation and 
plantings made before the last week in May sustained greater injury 
than fields planted later, whereas plantings made after the first week 
of June suffered little or no injury. In the two-generation area of 
New England the early and the late plantings sustained the heaviest 
infestations, irrespective of type or variety, whereas plantings made 
during the period from approximately May 20 to May 30 have, in 
general, escaped serious injury. Phenological observations are now 
in progress having for their object the application of plant-develop- 
ment phenomena as an indication of the most favorable planting 
period, irrespective of calendar dates, in order that the vagaries of 
the seasons may be discounted. 
Although the earliest planted fields of sweet corn have almost 
invariably sustained the maximum infestations in both the one and 
the two generation areas, thus indicating the possibility of using 
early planted sweet corn as a trap crop, actual attempts to apply 
this method of field control have thus far failed to show appreciable 
benefits, except under restricted conditions. 
QUARANTINE 
Quarantines have been established by the Federal authorities and 
by the various States concerned, which prohibit the movement out 
of infested areas of all plants and plant products which are likely 
