THE TEKRAPIN SCALE. 81 



spray injury than experiment 3, it is evident that the gasoline did 

 not tend to increase the spray injury. This experiment, in connec- 

 tion with experiment 3, shows that a 10 per cent emulsion of the 

 oil, even when used at the most favorable season, is too strong for 

 2-year-old trees whether used with or without gasoline. The for- 

 mula in experiment 7, while containing more oil than is required for 

 killing scale upon young trees, would undoubtedly be very effective 

 when used upon old trees, but owing to the effective results obtained 

 with 2 \ per cent of this oil in experiments 5 and 8, it was not thought 

 advisable to experiment further with the 10 per cent emulsion. 



In experiment 8 an emulsion containing 2| per cent of cottonseed 

 oil and 2} per cent of gasoline was applied to 28 vigorous 12-year-old 

 trees at Mont Alto, March 29, 1913, with very satisfactory results. 

 The interval between the application of this spray and the time of 

 making the scale count was too long to show the maximum effi- 

 ciency of the spray, nevertheless the mortality as shown is above 90 

 per cent and there was no spray injury. Observations made upon 

 the trees used in this experiment show that the oil content could 

 have been considerably increased without injury to the trees. 



Experiment 9, in which a 5 per cent emulsion of cottonseed oil 

 was carefully sprayed upon 16 trees at Mont Alto, Pa., gave unsat- 

 isfactory results. The mortality was about 50 per cent and the 

 spray injury was negligible. The oil in this case seemed to lack 

 penetration and spreading power. 



A comparison of the data in this experiment with that in experi- 

 ments 5, 8, and 10 shows that a 5 per cent emulsion of this oil is 

 satisfactory only when used with gasoline. Experiment 10 was the 

 last one performed with cottonseed oil. An extensive spraying was 

 made to test the efficiency of the gasoline and cottonseed-oil emul- 

 sion when applied in the fall. This experiment was successful and 

 showed that the terrapin scale can be attacked in the fall with satis- 

 factory results. Cottonseed oil, however, gives its best results when 

 applied in the spring. It is possible to increase the percentage of 

 cottonseed oil in this formula up to as high as 7 per cent without 

 noticeable injury to the trees. This increase in oil, however, adds 

 to the cost of the spray without greatly increasing its efficiency, 

 except for use on old trees with very rough bark. In this case it 

 may be found of advantage to use 7 per cent of the oil. 



LINSEED OH.. 



Five experiments against the terrapin scale were made with raw 

 linseed oil. The essential facts established in these experiments are 

 shown in Table XLI. 



Experiment 1 was made at Mont Alto, Pa., upon vigorous 11-year- 

 old trees that were nearly ready to burst into bloom. The same 

 20782°— Bull. 351—16 6 



