8 CIRCULAR 685, U. S. DEPT. OF AGRICULTURE 
drop and general maturity of the fruit increase. Not all fruits of a — 
given variety growing under the same conditions reach the full-ma-— 
turity stage at the same time, and under such condition late sprays 
would probably be effective in retarding drop of the least-mature © 
fruits. In view of the experimental evidence, however, it would seem 
reasonable to assume that, if the changes resulting in fruit abscission 
have advanced beyond certain limits, harvest sprays are ineffective in 
retarding the process and little or no control of dropping is obtained 
if a majority of the fruits have reached this stage. 
NuMBER OF APPLICATIONS 
Early results with harvest sprays (7) suggested the possibility that 
if additional retardation of drop is desired a second application could 
be made 4 to 7 days after the first application. In an experiment with | 
McIntosh designed to give information on this subject (2), it was 
found that a second application 3 or 7 days after the first spray ex- 
tended the effective period only 1 to 114 days beyond that resulting 
from the single application. With all treatments heavy drop set in 
12 days after the original spray was applied. 
The results of subsequent experiments along this line by various in- 
vestigators are summarized in table 2. It will be seen from these data 
that in only a few instances was there any appreciable benefit from a 
second application. The slight increase in effectiveness of the two 
applications in certain cases may have been due to a more thorough 
spray coverage. ‘The results presented in table 2 suggest that a single 
application, properly timed with the beginning of the drop, provides 
all the protection possible to achieve. Perhaps the strong tendency 
toward abscission as a result of advanced fruit maturity explains the 
failure of second sprayings to extend the protective period. In a few 
cases (table 2) where significant benefit was derived from two appli- 
cations as compared with a single spraying, it is probable that the 
first application was made somewhat ahead of the drop period. 
Taste 2.—Comparison of effectiveness of 1 and 2 applications of harvest sprays 
to apples of various varieties 
Spray im : 
; ies - 4 pples | State and literature 
Variety and picking date coucen: Spraying date dropped “a farGnee 
ee eee — ————_ — 
Jonathan: Dn Percent 
OR |S eS a ee ee 19.4 
Sept: 2% O Chae eee ae eee 8.4 
October 21_---------------- 10 sent SE Pecos GA bE aE a 4 | Ohio (4). 
OCHA SSN es ieee 8.3 | 
man Winesap: | 
el 0 eee ne eh, Set a int Rene eg eee 38. 1 
Och O ChAIG Se ee 20. 4 
October 30----------------- 10 Jot. ie et ea ee 39.5 Do. = 
Och IGS s 4th sete eae eS 22.3 
h: 
MelIntos re Deas eee Tae (phpeee oe 19.6 | 
September:4: sts 2= = 2 = 10 pes 16;YATE 285 eras eee 17.7 |}Washington (19). 
AStIDY Ah Ganesan See ae 
Ps Sra eed Ss tag eS ee , 
Septemberw0es) = 2. eas Sept. lsSepts be 2222 eee 5.3 | ew York (14). 
: { i? \ecohine et wamnmree coat 8 | 
September 11____--------__- 10 Soap ass NS SO ae 12.6 |New York (16). 
i pel ari Pale Genpact aaa 5.3 if 
Oise See el ee ea Se eee Fad 
September 25). -=-- 52-52 Sept: 157 Sept 182.452 = ee 4.7 | » 
3 10 (Sept. TE ahaha eee ne 2 2.9 
