20 STATION BULLETIN 355 



September 22 (Table 16) dropped less fruit in the succeeding eight 

 days than the controls. In this case it is apparent that the "hormone" 

 sprays were effective only in retarding the dropping of fruit which 

 had not previously received a "hormone" spray. The Mcintosh drop 

 seemed generally to be retarded immediately following the sprav of 

 September 10. There was as large a percentage drop from unsprayed 

 branches on September 16 as on sprayed branches on September 23. 

 The effectiveness of the hormone spray then decreased rapidly so that 

 an equal percentage of drop occurred on unsprayed branches on Sep- 

 tember 22 as on sprayed branches on September 25. Following this 

 date equal amounts of dropping occurred on spra3^ed branches two 

 days later than on unsprayed ones. 



Table 16. Per Cent Drops (cumulative) of Mcintosh after September 22 

 when Sprayed with Napthaleneacetic Acid 



Improved knowledge concerning the date, method of application, 

 strength and kind of hormone, and temperature of the air at the time 

 of spraying apparently explains in part wliy better results have more 

 recently been obtained in reducing pre-harvest drop of Mcintosh. In 

 1942 and 1943, Hoffman cf. al.^ ^\ found hormone sprays and dusts 

 equally effective in reducing the pre-harvest drop in New York. 

 Southwick^" i'^ found dusts less effective than spray in Massachu- 

 setts. Ellenwood and Howlett^, in Ohio, obtained favorable results 

 with commercial naphthaleneacetic acid on Stayman Winesap but not 

 Avith Delicious or Red Rome Beauty. Although Mcintosh was af- 

 fected Ijy the last spray, the fruit that remained on the tree was 

 overmature. 



Batjer and Marth^ present data for Mcintosh, Delicious, and 

 Stayman Winesap sprayed with naphthaleneacetic acid. They state, 

 "With this variety (Mcintosh) the effective period seems to be gen- 

 erally 10 to 12 days with one application." An examination of the 

 charts presented in their paper reveals that with only one hormone 

 spray Mcintosh apples were actually retarded from dropping for only 

 two days. Since this is the time interval between dates of equal 

 amount of fruit drop between treated and non-treated trees, this 

 would seem to be a conflict with their statement that the spray is ef- 

 fective for 10 to 12 days. Rather, it seems that the statement should 

 have been that heavy dropping began 10 days after the spray, was ap- 

 plied. Murphy ^^ also claims that the "effective" period of hormone 

 spray persisted for 10 days, whereas the data presented indicate only 

 that the fruit did not drop excessively for 10 days after spraying. He 



