240 SCHOOL ENTOMOLOGY 



and packing the top with a roller or beating it hard; or a 

 strip of sod may be prepared by scraping away the grass with 

 a scraper and then smoothing with shovels or hoes ; or a dead 

 furrow may be run and the oil line run on the smooth bottom. 

 In any case it is important to have a fairly smooth, hard 

 surface for the oil line so as to conserve the oil and make an 

 effective barrier. The oil line may be run by pouring the 

 oil from a watering-can with the mouth stopped down, 

 so as to make a line about the thickness of one's finger. 

 Along the outside of this line post holes, a foot deep, should 

 be sunk every few feet. The bugs crawling along the oil 

 line, which they will not cross as long as it is intact, will fall 

 into the post holes, where they will collect and may be crushed 

 or otherwise destroyed. In place of the post holes the bugs 

 collecting along the line have sometimes been destroyed with 

 a blast torch. Coal tar may be used instead of road oil, 

 but is more expensive and must be renewed more frequently. 



Where immediate action is necessary and road oil or 

 coal tar are not at hand, the corn may be protected in dry 

 weather by a dust furrow. Plow a deep furrow around the 

 field to be protected and thoroughly pulverize the soil by 

 dragging a heavy log back and forth through the furrow, 

 making the sides as steep as possible. Sink post holes every 

 few feet in the bottom. In attempting to climb this furrow 

 the bugs will slide back to the bottom and will collect in the 

 holes, where they may be killed. The dust furrow will be 

 of no value in showery weather and is most effective on light 

 soils in hot weather. 



For destroying the bugs which pass the barriers and for 

 those which may hatch on the corn, a spray of rosin soap, 

 one pound to six gallons of water, has been found very 

 effective, and should be used on the outer rows, so as to pre- 

 vent the field from becoming generally infested. 



