110 



zle. The thoro treatment of this acre and a half of corn required three 

 hundred and twenty gallons of spray, costing thirty cents an acre for 

 the soap and the labor of two men and a horse for a day and a half. 

 An examination of the treated corn three days later showed that about 

 75 percent of the bugs had been killed — apparently all that were ac- 

 tually reachedby the fluid. Those alive had evidently been protected 

 by the boots of the leases behind which they were hidden. The corn 

 showed nowhere any trace of injury. 



Field Experiments and Demonstration Fields 



Beginning in June, 1910. wheat fields heavily infested by chinch- 

 bugs and so situated as to be readily accessible to the farmers of the 

 vicinity were secured for experiments, and practical demonstrations 

 were made of the trap and barrier method, at first with coal-tar. later 

 with the two road-oils Xos. 6 and 7, and finally with crude creosote. 



Demonstrations witJi Coal-tar in 1910. — A demonstration field near 

 Oakdale, in* Washington county, gives us a good illustration of the 

 value of this method, with coal-tar as the medium. This was a twenty- 

 acre field of wheat sufficiently infested by both Hessian fly and chinch- 

 bugs to make it doubtful whether the crop would repay the harvesting 

 expenses. A barrier was made June 22. 1910, by plowing, smoothing, 

 and compacting a ridge on all sides of this field, digging post-holes to 

 a depth of eighteen inches at the edge of the ridge, at intervals of 

 twenty-five, fifty, and a hundred feet on different sides of the field, 

 and pouring a narrow line of coal-tar on the dry ground along the 

 center of the ridge in a way to touch each post-hole on the side farthest 

 from the field. This barrier, three quarters of a mile in length, was 

 kept up for eleven days, after which time so few bugs were left in the 

 wheat as to make further work unnecessary. The chinch-bugs accum- 

 ulating in the post-hole traps were killed with kerosene poured into the 

 holes, followed by sufficient water to float the oil to the top of the mass. 



The coal-tar sank so readily into the dry and dusty earth on the 

 first day that three applications were necessary, but two a day there- 

 after served the purpose, one made about seA'en in the morning and 

 the other at 2 :30 in the afternoon. These times were selected in order 

 to oppose a line of fresh tar to the chinch-bug during both morning 

 and afternoon movements. In the hot clear weather of these days the 

 chinch-bugs moved from 7 to 10 in the morning, but from 10 :30 to 2 

 in the afternoon there were practically none in motion except in 

 shaded places. The principal movement of the day. however, came, as 

 a rule, between 3 :30 and 5 :30 in the afternoon. 



Converting our data of cost of operation into expense per mile of 

 barrier — a line sufficient, that is, to surround a 10-acre field — reckon- 

 ing the farm labor used at $2 a day and the coal tar at the market 

 price of that season — $2.50 a barrel and freight from the nearest 

 point — we have a total cost of $23.11 per mile for the whole period of 



