8 IOWA AGRICULTURAL COLLEGE. 



less. By using only two nozzles, or by driving faster than the above 

 estimate allows, the expense would be lessened. It might do in 

 applying in this manner to reduce the emulsion to four per cent., but 

 beyond this I do not think it will do to go with any expectation of 

 getting satisfactory results. 



BURNING STUBBLE AND GRASS. On July 16th the stubble adjoin- 

 ing a corn field was observed to contain large numbers of bugs 

 traveling toward corn. In the afternoon this migration was going on 

 quite rapidly, and as the stubble was now quite dry it was fired with a 

 view to destroying the bugs remaining. Where tolerable thick and 

 when there was a fair breeze it burned quite readily, but it was 

 necessary to take some pains in carrying the flame along past thin 

 spots to keep it from dying out. A considerable portion of the field 

 however was successfully burned over, and the dead bodies of many 

 bugs not entirely consumed, which could be readily found on exam- 

 ination of the burnt area, testified to the destruction of hosts of the 

 pests. The bugs thus destroyed were mostly young larvae, the 

 majority of the adults, pupae and larger larvae having moved out. 

 The number destroyed must, I believe, have well repaid the little 

 trouble necessary to burn the stubble. 



Early in August the bugs had so multiplied in a field of Hun- 

 garian grass that no further growth seemed probable, and most of 

 the field was mown and the hay secured. A narrow strip was left 

 next the corn adjoining the field, the plan being to burn this as soon 

 as bugs began passing from the grass to corn. When the bugs 

 started, however, (August 13th) the grass was not dry enough to burn 

 except in spots. In such places as would burn, however, hosts of 

 bugs were consumed. This strip was at once mown, and after drying 

 a few hours another attempt made to burn it, as also on the following 

 day, but portions were still too green to burn rapidly, and unfortun- 

 ately for the experiment the two or three days following were not hot 

 and dry enough to render it fit to burn readily. A few days later, 

 however, on a dry day with a fair breeze, most of the strip remaining 

 unburnt was burned over, and examination showed that great numbers 

 of young bugs, even at this late day, were consumed. Bugs if 

 underground, or secreted in roots of stubble, will not be heated 

 enough to kill them, hence to destroy the greatest number as well as 

 to secure the most rapid burning, the fire should be started in the 

 hottest part of the day when bugs in greatest number will be 

 moving. 



OBSTRUCTING MIGRATION. The common method of checking 

 migration by making furrows often proves unsatisfactory, and several 

 tests were made to ascertain the conditions securing the most perfect 

 check. It was found that a single mark, two or three inches deep, 

 the sides of which were composed of fine dust, would form a com- 

 plete barrier to their progress; the bugs accumulating in the furrows 

 being utterly unable to crawl up the dusty sides. Any solid place, 

 however, which would give them a foothold, would permit them to 

 pass. 



A couple of furrows were plowed between grass and corn, and 

 pulverized by drawing a log along them, and the result watched. In 



