328 Agkioultdtbal Experiment Station, Ithaca, N. Y. 



luted kerosene, one tree with kerosene emulsion diluted with two and 

 one-third parts of water, and one tree was left untreated as a check. 



In the spring the mites appeared in force on the check tree, but upon 

 the treated trees not more than a dozen galls appeared during the 

 season, the pest having thus been nearly exterminated. The trees 

 treated with the undiluted kerosene were nearly killed, so that in this 

 form kerosene can not be used with safety on the pear. The only 

 apparent effect upon the trees treated with the emulsion, however, was 

 a slight retardation in the unfolding of the leaves in the spring. This 

 experiment was of course only an indicator but it gave tlie clue. The 

 result was not given to fruit growers at the time for it needed further 

 verification on a larger scale, and it was desirable to know what per- 

 centage of kerosene it was necessary to apply to do the work successfully. 



In September, 1892, we found sixteen quite badly infested trees in 

 the Horticultural orchard here at the Station. These were then labeled, 

 and March 10, 1893, all but two (which were left for a check) were 

 sprayed with kerosene 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 thoroughly from all sides with a knapsack sprayer. 



July 10, 189.S, trees were examined and it was found that the four 

 sprayed with the emulsion diluted with three parts of water were prac- 

 tically 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})er 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 shoAved 

 nearly as many galls as before. The two check trees were as badly 

 infested as they were the year before. 



These results showed that the emulsion was effective when diluted 

 with not more than eight parts of water, or containing about eight per 

 cent of kerosene. The remarkable success of these experiments could 

 be fully realized only by one who had seen the diseased trees in the fall 

 and again a year later. To illustrate it graphically one need but 

 imagine the four leaves shown in figure 1 (which were taken in the fall 

 and are typical specimens of the leaves on many branches of the trees 

 before they were treated) passed through some process by which all 

 of the galls could be removed except one or two on each leaf; this com- 

 parison does not exaggerate the difference between the trees before 

 and after treatment with the emulsion. In all of our work M'ith pre- 

 ventive methods against insect attacks, we have never met with more 



