February, '22] parrott: dusts for sucking insects 85 



One means of effective economy is to employ mixtures with the minimum 

 amount of nicotine necessary to secure satisfactory control. The ex- 

 periments as outlined indicate that for certain species of insects lower 

 ratios of nicotine may be used than now generally prevail. Of vital 

 importance in furthering an extensive emplo^Tnent of dusting for the 

 control of sucking insects is the need of less expensive materials which 

 function effectively as contact insecticides. 



Mr. Glenn W. Herrick. These experiments are interesting to me 

 as they point out clearly that in nearly any spraying operation, a certain 

 number of the insects escape, no matter how thoroughly you may carry 

 on the work. The efficiency of almost any insecticide in the field seems 

 to depend in the final analysis on the effectiveness with which it is applied 



President George A. Dean. The next paper on the program is by 

 J. S. Houser and C. R. Neillie, 



AN ACCOUNT OF THE SUCCESSFUL USE OF THE 



AEROPLANE IN DUSTING TALL TREES INFESTED WITH 



LEAF EATING CATERPILLARS. 



By J. S. Houser and C. R. Neillie 



(Withdrawn for publication in National Geographic Magazine, March, 



1922.) 



Mr. E. G. Kelly. What is the expense of this machine? 



Mr. J. S. Houser. The greatest item of expense lies in the original 

 cost of the plane, but when you consider that a Curtis plane can in these 

 times be procured for fifteen thousand dollars, and that some of the 

 liquid spraying machines used in New England cost five thousand dollars 

 and over, the comparison is not so much out of the way, after all. The 

 work that one can do in a day's time with an aeroplane equipped as was 

 ours, or equipped as a real machine for the work should be equipped, 

 will greatly exceed that of a liquid sprayer. Thus the saving in time 

 and labor would more than offset the original excessive cost of the 

 machine. 



Mr. F. C. Craighead. What is your idea of the best wind conditions 

 for application? 



Mr. J. S. Houser. We used a crossing wind. Under other condi- 

 tions you might want to fly directly into the wind. We found in our 

 trial flights at McCook field that we could get an excellent spread of the 

 poison by flying into the wind, and that would allow one to fly higher 

 than otherwise. 



Mr. F. C. Craighead. How far to the side did you fly? 



