80 BULLETIN 351, U. S. DEPABTMENT OE AGBICULTUKE. 



The spray used in experiment 1, which was made just before the 

 flower buds burst, was very effective as an insecticide. Every scale 

 that was covered with the spray solution was killed. Of 1,000 

 scales examined only 1.2 per cent were alive, and these were pro- 

 tected in various ways from the spray and were not completely 

 drenched. The spray injury was severe, however, owing to the 

 excessive amount of oil. 



Experiment 2 was made late in the fall with 2 per cent less oil. This 

 spray was very efficient against the scale, but the injury was more 

 pronounced than in experiment 1. The trees used in both experi- 

 ments required severe pruning and a liberal application of sodium 

 nitrate to restore them to their original vigor. 



Experiment 3 was made at Washington, D. C, to determine the 

 effect of this oil upon young trees. A vigorous 2-year-old tree was 

 thoroughly sprayed with a hand sprayer until all the scales were 

 wet with a 10 per cent emulsion of the oil. All the scales upon this 

 tree were destroyed, but the spray injury was so severe that the 

 tree died. It is worthy of note that this was the only tree killed 

 with oil during the two seasons' work. The increased tolerance of 

 the older trees to oil seems to be due entirely to the protection 

 afforded by their corky bark. 



Experiment 4 was also made at Washington. It shows that 

 cottonseed oil in a 5 per cent emulsion can be applied effectively 

 and safely to 2-year-old trees in mild winter weather. This formula, 

 however, does not contain enough of oil to make it effective against 

 the terrapin scale when applied on old trees, as is clearly shown in 

 experiment 9. 



Experiment 5 was also made at Washington, D. C. Two heavily 

 infested 2-year-old trees were sprayed with a 5 per cent emulsion of 

 equal parts of cottonseed oil and gasoline. A hand sprayer was 

 used and all the scales were thoroughly wetted with the spray. 

 Nine days after the application 98 per cent of the scales were dead 

 and no spray injury developed during the season. This spray was 

 also effective against scale upon old peach trees, as is shown in 

 experiment 8. 



In experiment 6 the amount of oil was reduced to 1.5 per cent and 

 the gasoline was increased to 3.5 per cent. The application was 

 made in the same manner and at the same time as in experiments 

 3, 4, and 5, but it was ineffective, owing to the small percentage of 

 oil. The high percentage of gasoline increased the wax-solvent 

 power of the solution and its narcotic power, but did not directly 

 contribute to its killing power. 



Experiment 7, in which 10 per cent cottonseed oil and 5 per cent 

 gasoline was used, gave practically the same results as 10 per cent 

 cottonseed oil when used alone. Since experiment 7 shows less 



