12s CIRCULAR 685, U. S. DEPT. OF AGRICULTURE oe 
tested. Experiments have also been conducted to determine the — 
compatibility of harvest-spray chemicals with a number of materials © 
commonly used in regular spray schedules. In this publication only 
the more extensively tested materials will be discussed. 
Table 3 summarizes the results obtained by a number of investi- 
gators relative to the addition of summer oil to growth-regulating 
sprays. While the results presented in table 3 are inadequate as 
proof, yet there seems to be a strong suggestion in most cases that 
the addition of a small quantity of summer oil increases the effective- 
ness of the spray. The increase may be due to any one of or a com- 
bination of three factors: (1) Increasing the solubility of the growth 
chemicals; (2) aiding penetration by maintaining an oil film of the 
substance in contact with the absorbing tissues; and (3) increasing 
the amount of growth substance available for absorption by increasing 
the deposit per unit area of tissue. 
TABLE 3.—I/nfluence of summer oil on the effectiveness of harvest sprays on apples 
| | Apples dropped when spray copaned drop- 
Spray the indicated percentage of oi ped : 
Variety | concen- | from Stateen al ee 
tration: lec Bese <r aN od need See ee ae ees | lee TTS ? 
| Ke sprayed 
0 0.125 | 0.25 0.5 1 trees 
P. p.m. |Percent |Percent Percent | Percent | Percent | Percent 
11.4 | 9.4 ile 
Rome Beauty__-___- Figs Rese lds Aas epee fof pepe NaS 55.0 |. Maryland (7). 
5 1 Nesta es aes coer rateee | Serie S tO em Peele ro 21.9 = a i (15) 
10 Do ale sey | Pe ha| peaches sl (SUG CAE 20. 2 ew York (13). 
MeIntosh_---------- 10 TASS AQ OD eee eee ae gl ee ee 24.3 | Massachusetts (23). 
10 SEDT| Sona ees A Deis Sake BE sae ere 24.3 | New York (12). 
WHEALt yee fase 5 Si4 a Bestar RS Gh ea A de ere eS 28.2 Do. 
Winesap a 10 3.2 DAG =| esata aie | eee ea 15.4 | Washington (19). 
WMehcious=222-42 52.22 DO xeh Aes AiG) Sate net ce ioe Teaeeals Oe 2.5 23. 1 Do. 
The fact that oil is objectionable in any spray just prior to harvest, 
particularly for fruit growers who follow a spray program that does 
not necessitate fruit washing, may be sufficient reason for avoiding its 
use with harvest sprays, despite the apparent increase in effectiveness. 
Worthy of consideration, however, is the use of as little as 1 pint to 100 
gallons (table 3). ‘The oil deposit on fruit receiving this amount can 
scarcely be detected, and there seems to be no objectionable modifica- 
tion of the quality of red color such as frequently occurs with higher 
oil concentrations. 
Because of the desirability of delaying harvest-spray applications 
until the beginning of the harvest drop, there are probably few in- 
stances in which harvest-spray chemicals could advantageously be 
added to the late cover sprays. Kadow and Hopperstead (6) pointed 
out, however, that under Delaware conditions fruit growers may some- 
times be required to apply a regular spray on midseason varieties so 
late that the harvest spray could well be combined with it. These. 
investigators found that a-naphthaleneacetic acid was as effective when 
applied with nicotine sulfate, Genicide, phenothiazine, or derris as 
when applied alone. However, in five different tests with the Deli- 
cious and Williams varieties, spray solutions containing lime were 
markedly reduced in effectiveness as compared with harvest sprays 
containing no lime. Overholser, Overley, and Allmendinger (19) 
also have reported reduced effectiveness with sprays containing lime. 
Available evidence indicates that growth-regulating chemicals enter 
