Notes on the San Jose Scale. 163 



allow the trees under experiment to remain midisturbed for the remainder 

 of the season and so watch the ultimate results of the applications, butt 

 owing to circumstances it became necessary to make the final records about 

 the middle of August, as follows : 



No. I. Insects apparently all dead. 



No. 2. A few insects alive. 



No. 3. Insects apparently all dead. 



No. 4. Insects apparently all dead. 



No. 5. Insects apparently all dead. 



No. 6, A few insects alive. 



No. 7. A few insects alive. 



No. 8. Insects apparently all dead. 



The condition of the foliage on all the trees remained essentially the 

 same as it was on July 19, when the notes recorded above were taken. 



Effects of whale-oil soap.— \x\ the light of these experiments, several 

 facts are conspicuous. It will bs noted that the first application of whale- 

 oil soap had little effect on the scale. From the results of the later appli- 

 cations, it is evident that the ineffectiveness was due in part, if not entirely, 

 to the poor physical condition of the soap solution. In the final examina- 

 tion of the trees treated with whale-oil soap, the fact was again emphasized 

 that a solution weaker than two pounds to a gallon of water cannot be 

 relied upon to kill the scale. 



Effects of kerosene. — Four different strengths of kerosene were used in 

 these experiments : pure, 20 per cent, 30 per cent and 7 percent. The pure 

 kerosene was the only strength which injured the foliage to any appreciable 

 extent, and in this case the injury was not sufficient to interfere with the 

 normal activities of the trees. From the fact, however, that a 20 per cent 

 mixture of kerosene and water gave equally as good results as clear kero- 

 sene in killing the scale, there seems to be no reason for using a stronger 

 mixture than this. This mixture (20 per cent,) has in no case, under my 

 observation, injured the foliage. 



The mixtures containing the smaller percentages of kerosene were less 

 satisfactory, though the final results of the 10 per cent mixture indicate that 

 good returns may result from the use of this strength. A 7 per cent mix- 

 ture, or I to 15, is evidently too weak to be effective, as live scales were 

 found on the trees so treated during all the time they were under observa- 

 tion. 



The kerosene and water mixtures were applied by means of a pump 

 having a kerosene attachment, thus using the ingredients in the form of a 

 mechanical mixture. Several pumps of this type are now on the market. 



As a further suggestion as to the use of pure kerosene, a word of caution 

 may be given. While no serious results followed the use of it in the cases 

 above noted, very conflicting results have been obtained by different experi- 

 menters, and by the same experimenters at different times. In many cases 

 no apparent harm has followed its use, while in others, for no obvious 



