39 
ditching, or the plowing of deep furrows in advance of the traveling 
hosts to entrap the larvae which will fall into them, and here they 
may be crashed by dragging logs or pieces of brush through the 
furrows. If feasible to till the trenches with water, or if they become 
partially tilled by rains, the addition of a very small quantity of 
kerosene, so as to form a thin scum over the surface of the water, will 
prove fatal to the caterpillars. 
Sometimes barriers of fence boards are erected, and the tops smeared 
with tar or other sticky substances, to entrap the larvae as they attempt 
to crawl over. 
Clean cultural methods and rotation of crops. — Rotation of crops 
should always be practiced, as well as the burning over of fields in 
the fall, when they are too badly infested to recover from injury. 
Above all other precautions which it is necessary to take to secure 
immunity from attack is that of keeping the fields free from volunteer 
grain and wild grasses, since experience shows that these are the favor- 
ite breeding grounds of the insect; in other words, they attract the 
female moths for the deposition of their eggs, and when the larvae 
hatching from these eggs have devoured the grain and grasses which 
grow in patches they are driven to cultivated fields for food. A perusal 
of the preceding pages will convince anyone that one of the most impor- 
tant sources of injury is the rotation of one cereal crop with another, 
or with grasses, and the planting of crops in fields that have been 
allowed to run waste to wild grasses and weeds. 
As grasses and cereals are the crops most affected by the fall army 
worm, the soil should always be very thoroughly plowed before plant- 
ing to any crop, particularly a similar one, and it is inadvisable (not 
alone on account of the fall army worm but on account of the numer- 
ous other common cutworms, wire-worms, and white grubs) to plant 
wheat, corn, or any other cereal in pasture land unless a crop which 
is not so subject to infestation by this insect intervenes. 
Fall plowing. — From the observed fact that hibernation takes place 
in the pupal condition in the infested fields, it follows that fall plowing 
is the most valuable of all preventives of injury, and is therefore 
always to be practiced where suitable to the crop, soil, and other con- 
ditions. In the case of perennial crops fall plowing is not applicable. 
For alfalfa Mr. Hunter has recommended that the field should be 
thoroughly "disked," or cultivated with a disk harrow, when practi- 
cally the same results will be obtained as would follow from plowing 
of other fields. For lawns a thorough going over with a long-toothed 
steel rake is the treatment recommended. Treatment of the soil by 
these methods serves to break up the cells in which the chrysalides are 
resting, as well as to destroy the insects in other stages in which they 
may be present in the fields. 
