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CIECULAE 17 5, TJ. S. DEPARTMENT OF AGEICULTTJEE 



An orchard test was made in 1925 to compare the 4 per cent casei- 

 nate oil emulsion with the 4° Baume lime sulphur. An examina- 

 tion of approximately 1,000 scales in each plat was made a month 

 after spraying, and at harvest time the total fruit from six pear 

 trees in each plat was examined, and the percentage of fruit that 

 was free from scale was recorded. The oil gave better results, both 

 in the percentage of scales killed and in the number of pears that 

 remained free from scale. The first examination showed that 99.9 

 per cent of the oil-sprayed scales were dead and that only 84.1 per 

 cent of those sprayed with lime sulphur were dead. At harvest 



time the pears were 96.1 and 88.8 per cent 

 free from scale, respectively. 



In comparing tests made on different 

 dates, no consistent difference in tox- 

 icity could be observed. In 1924 tests 

 were made about once a week from 

 February 26, when the trees were en- 

 tirely dormant, to April 4, when the 

 fruit buds were showing. In 1925 two 

 tests were made, one on February 24 

 and the other on March 13. The trees 

 were dormant at both times. Figure 1 

 shows the results obtained with emul- 

 sions containing 2 per cent of heavy 

 oils (No. 8 4 in 1924 and No. 9 in 1925) 

 on these dates. It is possible that 

 wind or other weather conditions fol- 

 lowing the tests may have modified 

 the results, but there is no evidence 

 of increasing or decreasing toxicity as 

 the season advanced. 



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SPRAYING EXPERIMENTS IN 1927 



FlG the E iS*KTSte*tSS3 Experiments were made in 1927 to 

 with 2 per cent heavy oil test the effect of several methods of 



emulsion on various dates, -, -n ,• -, ■> j> .1 1 tj- 



Takima, Wash., 1924-25 emulsincation, and also 01 the addition 



of Bordeaux mixture to the oil spray. 

 (Table 6.) A commercial apple orchard was used that had been 

 allowed to become rather uniformly infested with the San Jose 

 scale. The spraying was done March 28 and 29 with a power spray 

 outfit, using a pressure of 250 pounds. The examination of the 

 sprayed scales was made April 29, and the fruit was examined 

 October 4. As the owner of the orchard desired to obtain good con- 

 trol of the scale, it was not possible to leave any unsprayed trees, 

 and the percentage of unsprayed scales that were dead was deter- 

 mined shortly before the spraying was done. On account of the 

 heavy, uniform infestation in the orchard, there undoubtedly would 

 have been a high percentage of infested fruit if the trees had not 

 been sprayed. It is probable that most of the scales found on the 

 fruit were brought into the trees during the summer by birds and 

 by the wind. 



See p. 11. 



