g HARVEST SPRAYS FOR THE CONTROL OF FRUIT DROP 15 
a 
a 
| chief advantage of dusting would seem to be the rapidity and uni- 
| formity with which applications could be made. 
EFFECTIVENESS OF HARVEST SPRAYS ON PEARS 
Results with harvest sprays on pears, particularly the Bartlett and 
Bosc varieties, have been generally satisfactory. The use of harvest 
sprays on the Bartlett variety by Davey and Hesse (3) in California 
resulted in about a 50-percent reduction in fruit drop. These workers 
point out that commercial results with these sprays have been so gen- 
erally satisfactory that the use of them on Bartlett pears in California 
_ has become an accepted practice. Successful results with the Bartlett 
variety have also been obtained in Washington and Oregon. In har- 
vest-spray experiments reported by Gerhardt* fruit drop of this 
variety was reduced from 27 to 7 percent. 
In general, the time of application, spray concentration, and dura- 
tion of effect are essentially the same for pears as for most varieties of 
apples. 
: ie been occasional reports of harvest sprays advancing the 
maturity of pear fruits, but this has not been shown experimentally. 
As was pointed out in the case of apples, the effective use of these 
_ sprays will result in overmaturity of the fruit if it 1s not harvested 
at the proper time. This overmaturity of the fruit is not a direct - 
effect of the spray, but a result of fruit that would otherwise have 
fallen staying on the tree. 
EFFECTIVENESS OF HARVEST SPRAYS ON APRICOTS 
AND PEACHES 
Results with harvest sprays on stone fruits have been variable. 
Hesse and Davey (/0) obtained a significant reduction in drop of 
Stewart apricots. The effective period of the spray ranged from 3 
weeks in 1940, when applied at a concentration of 10 p. p. m., to as little 
as 1 week in 1941, when two half-strength applications (5 p. p. m.) 
were made. In these experiments an interval of 7 to 10 days intervened 
between the spray application and any noticeable response, a period 
considerably longer than the 1 to 3 days usual in the case of apples. 
Limited tests with harvest sprays on peaches have proved generally 
unsuccessful. Hesse and Davey (10), by using these sprays, obtained 
a slight reduction in the subsequent drop of Elberta peaches. These 
investigators conclude, however, that in no case did the sprays give 
differences great enough to suggest possible commercial use. Experi- 
ments with this variety at Beltsville failed to give beneficial results 
when the sprays were applied a few days prior to the harvest period. 
LITERATURE CITED 
(1) ne Tak: 
942. TEMPERATURE IN RELATIONSHIP TO EFFECTIVENESS OF PREHARVEST DROP 
SPRAYS ON APPLES. Amer. Soc. Hort. Sci. Proc. 40: 45-48, illus. 
‘and MArTrH, P. C. 
1941. FURTHER STUDIES WITH SPRAYS IN CONTROLLING PREHARVEST DROP OF 
APPLES. Amer. Soc. Hort. Sci. Proce. 38: 111-116, illus. 
(8) Davey, A. E., and Hesss, C. O. 
' 1942. EXPERIMENTS WITH SPRAYS IN THE CONTROL OF PREHARVEST DROP OF 
BARTLETT PEARS IN CALIFORNIA. Amer. Soc. Hort. Sci. Proce. 40: 
49-53, illus. 
4 GERHARDT, F. PHYSIOLOGICAL STUDIES ON BARTLETT PEARS AND DELICIOUS APPLES AS 
~ INFLUENCED BY THE PREHARVEST APPLICATION OF HORMONE SPRAY (ALPHA NAPHTHALENEACETIC 
| ACID). Summary of results for the 1942-43 season. (Unpublished report.) 
(2) 
