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destruction at harvest time by means of impassable barriers and lines 

 of post-hole traps placed beside infested fields of wheat. Altho winter 

 burning on a large scale proved impracticable in Illinois owing to wet 

 and snowy winters, small-scale field experiments with this operation, 

 under conditions locally and temporarily favorable, destroyed from 

 50 to 75 percent of the chinch-bugs under the harborage burned over. 



With a view to finding a better material than coal-tar for making 

 the barriers against the escape of chinch-bugs at wheat harvest, many 

 experiments were made in Illinois, in Texas, and in Arizona, with 

 various more or less similar substances, resulting in the selection 

 of a petroleum product, a residue of distillation, containing 70 

 percent of asphaltic materials and known as road oil No. 7. 

 This was virtually a perfect substance for its purpose, lasting from 

 five to ten or more times as long as coal-tar, without renewal. It had 

 the disadvantage, however, that it was not on the market, and must 

 be made at Whiting, Ind., solely for this special use; must conse- 

 quently be ordered some time in advance; and because of the delays 

 in transportation, was frequently received after the emergency for 

 which it was needed had passed. An attempt to secure the same re- 

 sults with a road oil of the same composition made at a refinery within 

 the infested district resulted disastrously because of the different phy- 

 sical qualities of this road oil, due to the different character of the 

 crude oil supplied to this refinery. 



A farmer's chance experiment made in 1912 showed that crude 

 creosote was almost as effective as coal-tar or the road oils. It had 

 the advantage that it could always be obtained without delay in any 

 desired quantity and from near-by sources of supply ; and this was the 

 substance principally used during the last year or two of the outbreak. 

 Experiments showed that creosote differed from coal-tar and the road 

 oils in the cause of its effectiveness, the latter being impassable be- 

 cause they were thick and sticky, and the creosote repelling the in- 

 sects by the odorous vapors given off. 



Field experiments with practical operations, especially in 1910, 

 1911. and 1912, showed that an effective barrier could be made and 

 maintained at an expense for labor and materials varying from $1.50 

 to $2 per day per mile, the difference depending mainly upon the 

 character of the season. 



Under certain conditions it is desirable to kill chinch-bugs by means 

 of an insecticide spray. Kerosene emulsion, in use for this purpose 

 since 1882, being difficult to prepare and dangerous to the plants 

 unless very carefully used, experiments were made to find other more 

 satisfactory substances, with the result that a tobacco extract known 

 as Black Leaf 40 was found highly effective in ratios of half an ounce 

 to a gallon of water in which half an ounce of soap had been dissolved. 

 Further experiments showed that soap solutions alone, three ounces 

 to the gallon of water, were almost equally useful. 



