PEAR LEAF-BLISTER MITES. 181 



After various experiments at Cornell University Agricultural 

 Station, two trees were chosen, of which one was treated with 

 kerosine emulsion diluted with two and one-third parts of 

 w^ater, the other tree left untreated as a check. "In the 

 spring the mites appeared in force on the check tree, hut 

 upon the treated trees* not more than a dozen galls ap- 

 peared during the season, the pest having thus been nearly 

 exterminated!" 



This was looked on only as a guiding experiment, and 

 carried on in the following j^ear on a larger scale, as follows : — 



"In September" (of the first year of observation, 1892) 

 "we found sixteen quite badly infested trees in the Horti- 

 cultural Orchard here at the Station. These were then 

 labelled, and on March 10th, 1893, all but two (which were 

 left for a check) were sprayed with kerosine emulsion diluted 

 with from three to ten parts of water. The trees were 

 standards varying from six to fifteen feet in height ; but it 

 was found that it required only about one and a half quarts 

 of the diluted emulsion, and about two minutes of time, 

 to spray a tree thoroughlj^ from all sides with a knapsack 

 sprayer. 



" July 10th, 1893, the trees were examined, and it was 

 found that the four sprayed with the emulsion diluted with 

 three parts of water w'ere practically free from the disease. 



" The four trees sprayed with the emulsion diluted five 

 times, and the four on which the emulsion diluted with eight 

 parts of water was used, showed a very few galls — not one per 

 cent, of the number on the trees the preceding year. 



" Two trees which had been sprayed with the emulsion 

 diluted with ten parts of water showed nearly as many galls 

 as before. 



" The two check trees were as badly infested as they were 

 the year before." 



From these experiments it appears, as summarized by Mr. 

 Slingerland, that the Pear Leaf-blister Mite can be nearly 

 exterminated by one spraijing of the Pear trees (at any time 

 after the leaves have fallen off in the autumn, and before the 

 buds have begun to swell in the spring) with kerosine emulsion 

 diluted with not more than five to seven parts of water — 

 the tree being sprayed thoroughly from every side, taking 

 especial care to hit ever}^ terminal bud, for this is where most 

 of the mites congregate. — (M. V. S.). 



* "Trees": two trees were dressed with undiluted kerosine, and nearly 

 killed, thus showing the necessity of being very careful in the use of kerosine ; 

 but as the dozen leaf -galls mentioned above were all to be found on the three 

 trees, the modified strength given in the emulsion answered well. " The only 

 apparent effect upon the trees treated with the emulsion was a slight retardation 

 in the unfolding of the leaves in the spring." — (M. V. S.). 



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