14. CIRCULAR 685, U. S. DEPT. OF AGRICULTURE 
Sor. MolsTureE 
Under conditions of soil-moisture shortage, fruit drop is usually 
a serious problem. Limited experimental evidence and general ob- 
servations indicate that harvest sprays are only moderately effective 
where such conditions prevail. 
RELATION OF HARVEST SPRAYS TO FRUIT MATURITY 
From 3 years of testing of a number of varieties of sprayed apples 
in storage Haller (9) concluded that apples given harvest sprays 
with o-naphthaleneacetic acid did not show any direct effect of the 
sprays on the firmness of the fruit, decay, or break-down, in 
comparison with unsprayed apples picked at the same time. It should 
be emphasized that with the effective use of harvest sprays a certain 
amount of fruit that otherwise would drop remains on the tree. 
Naturally these fruits are among the most mature, and if they are not 
harvested within a reasonable period their keeping quality may be 
seriously impaired. With summer varieties of apples the fruit is 
likely to become overmature if allowed to remain on the tree even a 
few days beyond the normal harvest period. Harvest sprays so com- 
pletely control dropping with many summer varieties that the early 
maturing fruits remain on the tree more or less indefinitely. If 
these fruits are not harvested within a day or two after they would 
have normally dropped if not sprayed, overmaturity may develop, 
particularly under high-temperature conditions. Under certain con- 
ditions and with some varieties, particularly Delicious and Stayman 
Winesap, water core is likely to develop, with subsequent break- 
down in storage, if the fruit is allowed to remain on the tree very 
long after the normal harvest period for the variety. On the other 
hand, general quality and storage life of the McIntosh variety under 
some conditions may be improved by allowing the fruit to remain on 
the tree for several days to a week longer than would be possible with- 
out the effective use of harvest sprays. However, if harvest is de- 
layed too long, with most varieties losses from overmaturity may 
offset any advantage obtained in added color and drop prevention. 
With many varieties it is likely that the harvest sprays will prove to 
have their greatest value in protecting the fruit grower from losses 
from dropping before and during the normal picking operation 
rather than in appreciably postponing the desirable harvest period. 
APPLICATION OF HARVEST-SPRAY SUBSTANCES BY 
DUSTING 7 
In 1941 and 1942 Hoffman, Edgerton, and Van Doren (14, 15) ob- 
tained equally satisfactory results on Williams and McIntosh apples 
with a-naphthaleneacetic acid applied in a tale dust as with this 
material applied in spray form. Equivalent amounts of e-naphtha- 
leneactic acid (equivalent to 10 p. p. m. concentration) per bushel of 
fruit were used in the two methods of treatment. According to the 
results of Southwick (27) with Oldenburg (Duchess) and Wealthy 
apples, dusting was not as effective as spraying, while with McIntosh 
the results from dusting were variable. 
Whether or not dusting as a means of applying harvest-spray sub- 
stances will prove to be generally as effective as spray with all vari- 
eties and under varied conditions remains to be determined. The 
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