CONTROL OF THE SAN JOSE SCALE O 



Table 2. — Results of experiments with lubricating-oil and lime-sulphur sprays 

 on the San Jose scale on apple trees, Yakima, Wash., 1924 



[Approximately 1,000 scales examined in each test] 



No. 



Material used 



Dilu- 

 tion 



Tests 

 made 



Scales 

 dead 



Con- 

 trol 



1 



Lubricating-oil (red engine) 1 emulsion (soap emulsifier) 2 



Per cent 

 oil 

 2 

 3 

 4 

 2 

 3 

 2 

 3 

 2 

 °B. 

 4 

 5 



Num- 

 ber 

 6 

 1 

 1 

 6 

 1 

 6 

 3 

 7 



2 

 2 

 6 



Per cent 

 98.2 

 99.6 

 99.9 

 96.7 

 99.5 

 95.4 

 99.6 

 96.3 



95.8 

 93.7 

 19.1 



Per cent 

 97.8 



? 



Do .._ 



99.5 



3 



Do . 



99.9 



4 



s 



Lubricating-oil (brown neutral) 3 emulsion (soap emulsifier) 2 



Do 



95.9 

 99.4 



6 

 7 



Lubricating-oil (brown neutral) 3 emulsion (casein emulsifier) 4 . -_ 

 Do . 



94.2 

 99.5 



8 





95.4 



9 



Commercial lime sulphur, 32° Baum§ 



94.8 



in 



Do 



92.2 



11 



Check 













1 See specification No. 8 (p. 11). 



2 See formula No. 1 (p. 9). 



3 See specification No. 6 (p. 11). 



4 See formula No. 2 (p. 9 ). 



5 See formula No. 3 (p. 10). 



While Table 2 indicates that better control was obtained with the 2 

 per cent oil sprays than with the lime sulphur, from 2 to 4 per cent 

 of the scales survived, and this is too large a percentage for effective 

 control. Although lime sulphur allows a small percentage of scales 

 to survive, it was found that these frequently do not reproduce, even 

 though they may live until the middle of the summer. 3 This applies 

 only to the scales that have been actually covered with the spray and 

 have survived. Those not sprayed reproduce as usual. This does not 

 seem to be the case with oil-sprayed scales; hence with oil it is 

 necessary to approximate 100 per cent kill of the scale in order to 

 control it. Of the 25 tests made with a 2 per cent oil, and recorded 

 in Table 2, tests 1, 4, 6, and 8, only 7 were satisfactory. In these 7 

 less than 1 per cent of the scales survived, but on an average these 

 tests allowed too many scales to live for good control. The few tests 

 made with oils at greater strengths indicated that dilutions of 3 or 4 

 per cent would be sufficiently effective for good scale control. Little 

 or no difference was evident in the effectiveness of the emulsions made 

 with soap or with casein spreader and those made of the miscible 

 oils. There is also very little difference in the effectiveness of the 

 heavy (red engine) and light (brown neutral) oils. 



At harvest time fruit was examined for scale in an orchard part of 

 which had been sprayed, while the trees were dormant, with lime 

 sulphur, part with a 2 per cent caseinate oil emulsion, and part with 

 a 3 per cent caseinate oil emulsion. There had been a light infesta- 

 tion of the scale in the orchard, but the infestation was not sufficient 

 to furnish counts in the spring. Three or four thousand apples were 

 examined in each portion of the orchard. In the trees sprayed with 

 lime sulphur 0.23 per cent of the apples were infested with the 

 scale, in those sprayed with the 3 per cent caseinate oil emulsion 

 0.49 per cent of the apples were infested, and in those sprayed with 

 the 2 per cent emulsion 1.36 per cent of the apples were infested. 

 This indicates that the lime sulphur is effective, and also that the 



3 Newcomer. E. J., and Yothers, M. A. sterility in the san jose scale. Jour. 

 Econ. Ent. 22 : 821. 1929. 



