STATE HORTICULTURAL SOCIETY. 167 



liave no ettect whatever on the scale insect, whenever they may be apphed. He also 

 believes that petroleum or kerosene oil, or probably any oily or fatty substance, will 

 most ctieetually kill every bark louse and its eggs that it may come in contact with, 

 without injuring the trees, and cites in proof of the efficacy and harmlessness of oleagin- 

 ous applications, the experiments of Dr. Mygatt, who used lard in 1854, of Dr. Fitch; 

 who used grease or oil; of Mr. Cavanach, of Brooklyn, who used kerosene; of Mi*. J. L. 

 Budd, of Iowa, who used benzine and soap, and of Dr. Pennington, who applied pure 

 petroleum to the trunks of one hundred trees without injurious effects. Immediately 

 iu the same connection Mr. Walsh gives the opinions of other men in ditferent places 

 to the contrary, who had killed trees and other vegetables with oils, and concludes 

 that nothing but actual experiment will settle the matter, which he promises to do in 

 the following year, i. e., 1868. After this time^ when he hoped to complete his 

 •experiments, Mr. Walsh, in February, 1869^ at Aurora, before the Northern Illinois 

 Horticultural Society, declares that the best remedy he had found against bark lice 

 was one part domestic soap and six parts of water, to be applied, as I have heretofore 

 set forth, soon after the insect is hatched. From these reports, in the absence of 

 further evidence, it is probable that Mr. Walsh did not tind, after all, that oleaginous 

 applications were reliable. 



For my part, I can say nothing about it from actual experiments. Grafting men 

 and others tell me that oils invariably injure young scions. I confess that I have no 

 belief that fatty oils can be safely used, except it may be in moderation on the 

 thickened dead epidermis of ^the trunks of rough old trees, and there it can do 

 good, because the bark louse can only be found thriving on somewhat tender bark, 

 and best on the young tender branches, where fatty oleaginous applications, without 

 doubt from the evidence, would be entirely ruinous. 



In all our experiments it becomes us to be very cautious lest we be led into eiTor 

 from the many causes that might be at work silently and unobserved destroying the 

 bark louse. And like the maxim of 3Ir. Paget, the great English surgeon, who upon 

 seeing good results after administering a remedy for disease, asks himself the question, 

 what would have happened if he had not given it? 



This I appreciated most forcibly in 1867 while I observed the work of the acarian 

 parasite at the same time that I was experimenting with soaps, corrosive sublimate, 

 •etc., and finally the great work the parasite was doing led me for the time to desist 

 from experimenting. Had I not discovered the parasite, uiy applications would have 

 been lauded as eminently successfid, and the following year the parasites were so 

 lunnerous that experiments would have been still more uncertain. Kerosene and 

 other volatile oils may not always kill the trees, and may also fail to kill the lice. 



About three years ago Mrs. Shinier had pure kerosene applied to two trees iu Mt. 

 Carroll Seminary orchards with great care to every limb and twig, in the spring, before 

 the appearance of the leaves. The trees have not been materially injured; have 

 fruited since, but still have many bai-k lice on them. One tree badly infested with 

 bark lice on body and limb was headed in closely so as to make sure work. The 

 trunk and limbs were most faithfully treated with a mixture of kerosene and tobacco 

 •decoction, thought to be strong enough and greasy enough to kill all the lice if there 

 was any kill to them; and yet when the young shoots came out they were found to 

 have bark lice on them, and now the hmbs are about as badly infested as other trees 

 •of the orchard, and moreover the body of the tree, which was very healthy when the 



