20 



THE SURFACE AND COAL-TAR METHOD. 



The objections made by farmers to the use of most of these bar- 

 riers is that the finest pulverized soil soon becomes incinisted by even 

 the shghtest rainfall and the bugs then pass over it without difficult)', 

 while barriers of boards are expensive. It is feasible to eliminate 

 both by simply smoothing off a path along the margin of an 

 infested field where such an one adjoins the one to be protected. 

 This can be done with a sharp hoe, and as the margins of wheat 

 fields usually become compacted, it is but little trouble to thus 

 clear off a path a foot or more in width, smooth as a floor, with 

 the surface almost as hard. Along this path circular post holes 

 are sunk, as in the bottom of furrows, and a train of coal tar is run 

 between them, being so arranged that it will reach the post hole 

 at the edge farthest from the field from which the bugs are migrat- 

 ing. The bugs, on reacliing the train of coal tar, will follow along 

 until they reach the post hole, while those meeting with the post 

 hole will usually divide and, following around it, join with the 

 flow of bugs moving along the train of coal tar. The result is that 

 they become congested in the acute angle where the coal-tar train 

 is intercepted by the post holes. Those in the apex of this angle 

 can not turn back, and thus are continually pushed into the post 

 holes b}^ those behind. As the bugs, varying from the red larvae 

 of the younger stages to the almost black ones of the last stage, 

 mass along the line of coal tar, they have much the appearance of 

 a reddish-brown stream running into the holes. From these holes 

 there is no escape and here the bugs can readily be killed by sprinkling 

 with kerosene. The slightest train of coal tar is sufficient to obstruct 

 the passage of the bugs, and light rains will not affect its efficiency. 

 In dry weather these trains of coal tar soon become covered over with 

 dust and must be renewed; but in showery weather there is no dust, 

 and if the coal tar is renewed daily or, at most, twice each day, it will 

 accomplish its work and nothing further will be needed than to kill 

 the bugs that have collected in the post holes. This measure is inex- 

 pensive and can be promptly put into operation if the coal tar is at 

 hand. The writer has been able in this way to effectively protect a 

 field of corn bordered on two sides by a wheat field literally overrun 

 with chinch bugs at harvest and during a time when light showers 

 were occurring, frequently several times each day. 



THE RIDGE AND COAL-TAR METHOD. 



Differing quite materially from the preceding are the various com- 

 binations of coal tar and ridges of earth, smoothed and packed along 

 the apex, or, instead of the ridge of earth, 6-inch boards, such as are 

 ordinarily used for fencing, placed on edge and the upper edge coated 



[Cir. 113] 



