DUST SPRAYING. 475 



they are cheaper to manipulate than the Hquid spraying machines. 

 I have reason to doubt that statement. The best result is obtained 

 in the morning when the dew is on the leaf. That is about the only 

 feasible time to do the work, otherwise the first strong wind will 

 blow it all away or will blow it ofif from one side of the trees. 

 Another feature is that you have to be careful not to let that powder 

 get to the horses. I do not believe that the dust spray is as effective 

 for plant life as kerosene emulsion. It is not so effective and does 

 not stay on as long. Mr. Johnson is a member of the firm that 

 manufactures these machines and is very enthusiastic, of course. 



Mr. Carbine (Ore.) : Many of our orchards are located where 

 there is no dew, and this dust will not stick where there is no dew, 

 so I do not see that it would be of any value to us whatever. This 

 question was discussed at our meeting last June at Portland, and a 

 professor was there who stated it would not stick to the leaves unless 

 there was dew, and that is something we do not have in eastern 

 Oregon. 



Prof. A. T. Erwin (la.) : At the Iowa experiment station we 

 have been giving some attention to dust and liquid spraying, and 

 the opinion our way is that if we are dealing with some leaf-feeding 

 insect, such as the cabbage worm or potato bug, the dust spray will 

 give good results much cheaper, is just as effective and more easily 

 applied. On the other hand, if you have fungous disease or codling 

 moth it is not so effective. At my home in central Missouri the dust 

 spray first came into use, and I have talked with many of the largest 

 growers, and I know scarcely any of them that regard it as being 

 equal to or better than the liquid spray. Sometimes it is the question 

 of that or nothing. On rolling and steep land you cannot get at the 

 trees with liquid spray, and on such land it is the only thing they can 

 use. It is better than nothing. That is the consensus of opinion 

 among the large growers. 



Mr. Yahnke : When I was at St. Louis I met Mr. Johnson. He 

 told me more than what was in the paper, but another gentleman 

 whom I met at the same time talked better than Mr. Johnson. He 

 said the result from dust spraying depended entirely on the prepa- 

 ration of the dust. He said there was scarcely one out of ten who 

 had ever tried dust spraying that could make a good dust. That 

 was the difficulty in using it, the using it right. For instance, it is 

 not right to make a spray of Bordeaux by mixing the blue vitriol and 

 the lime. First you have got to get the lime to dust, the lime has 

 got to be slaked and then made into dust and the blue stone added, 

 all powdered and dried in a dry kiln and then mixed. The only 

 good results gained from using" the dust were by using it right. 



The President : Did he say where you could buy the dust in that 

 form? 



Mr. Yahnke: No, he did not, but I would prepare it myself 

 I experimented a whole day to get a batch right. I make the du£ 

 and then buy the blue vitriol and dry it myself, and then mix it 

 myself and apply it in that way. There are a good many orchards 

 in our state that are so hilly that we cannot get at them with a liquid 



