PREHARVEST APPLE DROP 



19 



Table 14. Differences in Per Cent Drop Between Mcintosh Sprayed with 

 a Commercial 'Set' and Unsprayed Trees 



Hormone in 



warm water 19 



Minus Hormone in 



cold water 29 



_8.0** -16.6** 1.7 



19.1* 1.4 



Significant to 5 per cent point 



Significant to 1 per cent point 



to the inference that the differences in drop in 1941 were possibly due 

 to factors other than spray treatment. 



A carefully controlled test was made in 1940 on selected branches 

 of two Mcintosh trees. The fruit, pedicels, and spurs were thorough- 

 ly sprayed during the warmest part of the day with the same com- 

 mercial product used in the previously reported"^ test. The treatments 

 were as follows : On September 10, at the first sign of dropping, all 

 branches except the controls were sprayed. These branches were 

 again spra^^ed on September 22, also some other branches were 

 sprayed for the first time. The apples attached to the branches were 

 counted immediately following spraying and on several later dates. 

 From Table 15 it may be seen that dropping was retarded only for 

 the first six days following the spray application of September 10. 

 Outstanding is the variation between branches on the same tree and 

 between different trees in response to the hormone spray. Hitchcock 

 and Zimmerman'^, using soray made up of derivatives of naphthalene- 

 acetic acid, also found differences in response between trees of the 

 same variety and between branches of the same tree. 



Although trees sprayed on September 10 were not further bene- 

 fitted with relation to fruit dropping by a second spray application 

 made on September 22, those branches sprayed for the 'first time on 



Table 15. Per Cent Drops (cumulative) of Mcintosh when Sprayed 



with Napthaleneacetic Acid 



