156 Report of State Board of Horticulture. 



Dead and living scales were first counted on these trees the following 

 day, March 4. Although the fact was not known at the time, it became 

 apparent later by comparison of percentages of scales on these trees with 

 those found on check trees and on other lots counted before insecticide 

 treatment that no discoverable effect of the insecticide had been produced 

 at the time this first count was made. If any scale insects had been killed 

 so soon, their appearance had not yet sufficiently changed to indicate the 

 fact. The percentages found on this first day are, consequently, to be 

 taken as indicating the ratio, before treatment, of dead and living scales 

 among the young of the preceding year. One thousand three hundred and 

 fifty such scales were counted in all, and fifty-two per cent of these were 

 alive, forty-eight per cent having died from unknown causes, in most 

 cases probably from drouth. 



In determining the effect of the insecticide under the varying conditions 

 supplied, this first count of living scales was made the starting point for 

 the calculation of the percentages of scales killed; that is, if only fifty 

 per cent of the scales were found alive at the beginning of the experiment, 

 the destruction of scales by the insecticide was figured on this fifty per 

 cent, those dead in the beginning being, of course, ignored. Counts were 

 made upon carefully selected specimen twigs or branches, the number 

 counted each time varying from one hundred to four hundred, and the 

 totals for each tree, from three hundred to one thousand three hundred 

 and fifty. The total number of scales counted from tnis lot on nine trees 

 was nine thousand. 



The effect of the insecticide was only gradually made manifest, and 

 was, as a rule, not fully produced until about the tenth day, although the 

 difference between the final result and that apparent at the end of the 

 first week was really but small. Consequently, in describing the different 

 features of the experiment, the average of the counts after the first week 

 will be taken to express the final effect of the insecticide in destroying the 

 San Jose scale. 



As these various trees were treated subsequent to the insecticide spray 

 by an application of various amounts of water at different intervals, it 

 will be necessary to discuss each tree separately. 



