June, '21] MOORE: spreading of sprays 253 



In the spraying work, a strong repellent will be used, with which the 

 vegetation will be kept coated throughout the beetle season. For 

 practical results, it is essential that the roadside vegetation along the 

 main traveled roads throughout the infested territory be kept in a 

 condition as little attractive to the beetle as possible, so as to offer the 

 least favorable conditions for the insects to feed and congregate there. 



In connection with the insecticidal investigations, large scale spraying 

 experiments will be undertaken during the coming season, for the final 

 testing of killing agents against the beetles, in anticipation of renewed 

 control spraying another season, if the materials tested react favorably' 



Summary 



For the past two seasons, greatest emphasis has been placed on eradi- 

 cation or control of this insect. The work has now been reorganized 

 more particularly along an experimental basis, looking forward to the 

 time when active control work can again be undertaken on a compre- 

 hensive scale, with some assurance of reasonable success. In addition 

 to the experimental work, parasite importation, breeding and dissemina- 

 tion will be pushed vigoroiisly, to hasten the day when the parasites 

 and predaceous enemies of the beetle may become an important factor 

 in keeping the pest within reasonable bounds and comparable with other 

 native pests. Meanwhile quarantines will be enforced as efficiently 

 as possible, along with other restrictive measures, in an effort to delay 

 and hinder the spread of the insect. 



President Wilmon Newell: The next paper is 

 THE SPREADING OF SPRAYS 



By William Moore, St. Paul, Minn. 

 (Withdrawn for publication elsewhere) 



Mr. C. L. Metcalf: I would like to ask how to measure the sur- 

 face tension which is so important in this sort of work. 



Mr. William Moore: It is hardly worth while to measure the 

 surface tension of the liquid, since the interfacial tension comes into 

 play. I have not given any figures of the interfacial tension because 

 it has not been possible to measvire the interfacial tension of the leaf 



