172 Report of State Board of Horticulture. 



ence to those alive when the experiment began, we find that the ratio of 

 scales still living on these eighteen trees on the 12th of May varies from 

 none at all for five of the trees to two and seven tenths per cent for one 

 tree, the average ratio of living scales for the eighteen trees being a little 

 less than eight tenths per cent. 



In preparing bulletin 71 I had no data in hand for a comparison of the 

 insecticide effects of the lime and sulphur washes with whale-oil soap 

 or petroleum, but Mr. Titus's visit of May 12 enables me to make good 

 this deficiency. All the infested trees at this place not used in the experi- 

 ment had been sprayed with whale-oil soap in March by one of my regular 

 field parties, and an examination of five thousand scales on eighteen of 

 the trees so treated gave a total of thirty-nine scales, a little more than 

 twice the ratio of living to dead scales found on those which had been 

 treated with the lime and sulphur washes. 



From the foregoing it appears that certain of the statements made in 

 bulletin 71 must be modified with reference to these later and more com- 

 plete results. It may be safely said that the washes applied were ex- 

 tremely efiicient insecticides. Even such failures to kill the scales as 

 occurred were probably due to imperfect distribution of the spray. The 

 action of the washes is more prolonged than I have been previously led 

 to infer, extending evidently beyond three weeks, and although at first 

 considerable, differences were noticeable between the Oregon and Cali- 

 fornia washes, we must conclude from the above report that these are dif- 

 ferences in promptness and rapidity of action rather than in the final effect. 

 A similar statement may be made with reference to the effects of rain as 

 represented by the application of water to our experimental trees. This 

 clearly has the effect to delay, but not to prevent, a complete destruction 

 of the scale, and it is apparent that these western washes, costing $1.12 

 per hundred gallons, are at least as destructive to insect life as the solu- 

 tion of whale-oil soap, costing 36.50 for the same quantity. 



The following table will give some details of observation not reported 

 in the text. The numbers used for the trees are the same as those in the 

 tables of bulletin 71 and the experimental history of each tree can 

 also be found in that bulletin. It is to be understood that five hun- 

 dred scales were counted for each tree May 12. The first tree of 

 each pair was sprayed with the California wash, and the second with the 

 Oregon wash. 



