232 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



are in a battle and our enemies, these diseases and insects, are not follow- 

 ing any fixed dates. The insects emerge and lay their eggs and pass 

 from one stage to another depending upon temperature and other condi- 

 tions. Our fungi germinate their spores with reference to moisture 

 and temperature. We, as experimenters, have got to know just when 

 the critical stage is when we can deliver our broadsides most effectively. 

 What we want to do is to put ourselves in the grower's place to work out 

 a method of disease control and insect control that will be effective and 

 cheaper than the present method. If that calls for six applications of 

 dust or eight applications of dust when the standard nimiber of sprays 

 is three or four, let's do it that way. The real test of the relative merit 

 of the two methods comes from the economic standpoint. Can we con- 

 trol insects and diseases more effectively and more cheaply by a method 

 of dusting than by a method of spraying? 



President Wilmon Newell: The entire subject is now open for 

 general discussion. 



A Member: I should like to ask Mr. Giddings with reference to the 

 various dusts applied, whether the materials that were used to secure 

 adhesiveness were successful. If so, which was the best? 



Mr. N. J. Giddings: They were not particularly successful. The 

 Venetian Red was used not particularly to secure adhesiveness but to 

 help in carrying the material through. It gave evidence of other 

 trouble in the machine which I do not think would warrant its use. 

 The others we did not think were worth while. 



A'Ir. William Moore: I presume that in the experiments with nico- 

 tine dusts the half percent, of nicotine given is the total nicotine found in 

 the dust. We all know the principle of the gas mask — a finely divided 

 solid through which the air was drawn to the soldier; the poison gas 

 never reached him, as it was adsorbed by the solid. Any solid which is 

 finely divided and presents a large surface may adsorb certain liquids, gases 

 or even other solids. In this particular case there is a possibility of 

 the adsorption of nicotine, thus locking it up and making it unavailable. 

 Another question is that nicotine sulphate itself is non-volatile. How 

 was this loosened up? I don't suppose that the nicotine would become 

 effective against the insect until at such time as it became volatile. 

 You thus have two possibilities of reducing the amount of nicotine that 

 was actually effective against the insect. When we consider the cost of 

 nicotine it is not advisable to lock up any in such a way. 



I wish to point out that different materials will give you different 

 results. I know nothing about it, but would assume from the nature 

 of the materials that a sulphur with nicotine added would have more 



