SPRAYING TO CONTROL APPLE DROP 5 



was made to "wet" each apple stem. To do this, it was iiecessarj' to use 

 from 15 to 40 gallons of spray per tree depending on the size of the tree 

 and crop and somewhat on the density of the foliage. A small amount 

 of summer oil (1 pint to 100 gallons) was included as a spreader in a few 

 of the spray applications. No unforseen difficulties developed in actual 

 spraying operations. A few growers have reported trouble due to excess 

 foaming of some commercial hormone preparations. One grower reported 

 some wear of leather gaskets, but it was not possible to trace this to the 

 spray material. In case of any such injury, the fault would lie with the 

 carrier. The active hormone itself would not be deleterious. 



EfTective Period of Hormone Sprays 



The influence of hormones on the dropping of fruit is not manifest 

 immediately following application. An interval of from 1 to 5 days elapses 

 before any effect becomes evident or measurable. In these tests, the 

 interval was usually 2 or 3 days, thus making the effect of the hormone 

 on rate of drop discernible on the third or fourth day after spraying. It 

 should not be assumed on the basis of this statement that dropping de- 

 creased suddenly and markedly at any particular time. In all the tests 

 with Mcintosh and Wealthy, the lessening of dropping usually was not 

 apparent in the field to the casual observer, especially where treatments 

 were randomized. This was due not only to variations in apparent effec- 

 tiveness between trees within treatments, but often to the considerable 

 differences in total yield among the trees. With Duchess of Oldenburg 

 and an unnamed variety maturing in late summer, the effects were readily 

 apparent and hardly needed yield and drop figures for confirmation. Table 

 1 illustrates a case of very effective control from the application on August 

 20 of a commercial hormone spray containing 10 p. p.m. of hormone and 

 used at the rate of about 15 gallons of spray per tree. 



T.\BLE 1. — Dropping of Duchess of Oldenburg 

 Average numbers of dropped apples per tree picked up during the ripening 



period. Test 8. 



Aug. Sept. Average No. 



21 22 23 24 26 27 29 31 2 3 of apples 



per tree 



Sprayed 52.7 18.3 6.7 1.8 2.0 2.7 1.8 3.5 12.0 3.0 1095 



Check 74.8 19.0 26.0 19.6 31.8 19.0 48.4 80.0 230.0 225.0 1198 



Total drops per tree from August 23 to September 3 amounted to ap- 

 ))roximately one peck for the sprayed trees and over 5 bushels for the 

 checks. Many of the apples were over-mature when picked on Septem- 

 ber 3. 



Other fall varieties such as Williams, Melba, and Early Mcintosh are 

 reported to react similarly to hormone spraying. 



After the effect is initiated, the length of time that it will be maintained 

 depends greatly on the variety. As far as Duchess was concerned, the 

 apples held on even after internal breakdown had commenced. Table 2 



