67 



and other parasites upon our plants and trees without injury to them; 

 and it has frequently been stated that crude petroleum has been used 

 for the same purpose with good effects. Gas tar has proved injuri- 

 ous." (Ibid. March 30, 1866.) Two years afterwards the same man 

 speaks in the following manner of petroleum: — "If any one wants 

 to kill his trees, let him use petroleum ; yet it is beneficial in a diluted 

 state when applied to shrubs and plants to keep off insects, but it is 

 death when applied to the roots." {Ibid. January 10, 1868.) 

 Whether these observations are intended to apply to kerosene as well 

 as to petroleum, is more than I can say. 



At the Meeting of the Iowa State Horticultural Society, Octo- 

 ber 19, 1867, Mr. J. L. Budd, a fruit-grower residing at Shellsburg, 

 Benton Co., Iowa, stated that he "had found 10 parts of benzine and 

 4 of soap the best remedy against Bark-lice." The benzine would 

 in all probability be effectual at any time of the year ; but, as I think 

 I have shown, the soap would be useless, except early in the summer 

 and except also by its diluting the strength of the benzine. 



Finally, Dr. Pennington, of Sterling, Whiteside Co., Illinois, 

 told me in 1867, that he had applied pure petroleum to the trunks 

 of about 100 apple-trees infested by the Oyster-shell Bark-louse, and 

 to about one-half of such of their limbs as were 1^ inches and over 

 in diameter; and that he can perceive no injurious effects. Before 

 applying the petroleum, he pruned the trees well. 



I think that there can be no doubt whatever, that petroleum, 

 kerosene, benzine, lard, and generally any kind of animal or vegetable 

 oil, will kill Bark-lice at any time of the year, though all kinds of 

 watery infusions fail to have any effect upon the matured scale. The 

 reason is obvious. The eggs under the scale can only be killed by 

 some substance capable of reaching them through the protecting scale, 

 which is glued too firmly and closely to the bark to allow of anything 

 penetrating underneath it. Now, nature has made the scales rain- 

 tight; but, as we have no showers of oil, she has not thought it neces- 

 sary to make them oil-tight. Hence, oily substances will soak through 

 the scale, and reach the culprit eggs; but watery infusions are in- 

 capable of doing this. 



Wliether some or all of these oily applications may not be more 

 or less injurious to vegetable life, is a much more doubtful and dis- 

 putable question. I saw an account in the New York Tribune several 

 years ago, of a whole orchard being killed by applying "tanners' oil" 

 to it, whatever that kind of oil may be. Perhaps it might have been 

 applied in exorbitant quantities. Again : I have known a plum-tree 

 killed by saturating a large cloth with kerosene, and wrapping it 



