HARVEST SPRAYS FOR THE CONTROL OF FRUIT DROP 5 
SOURCE OF SPRAY MATERIALS 
Tn all the experimental work carried on at Beltsville the pure chem1- 
-eals were dissolved in small quantities of ethyl or methyl alcohol and 
added directly to the water in the spray tank. a-Naphthaleneacetic 
acid, the sodium salt of a-naphthaleneacetic acid, or o-naphthalene- 
acetamide, as supplied by several reliable chemical companies, can be 
used as indicated. Since, however, these chemicals are not readily 
soluble in water and it is not practicable for growers to measure 
accurately the small amounts necessary, several proprietary commer- 
cial preparations * have been placed on the market in convenient form 
for use by orchardists. These preparations consist of weighed 
amounts of active chemicals mixed with powdered fillers or lquid 
solvents designed to facilitate quick solution and uniform mixing 
when they are added to the spray liquid. 
FACTORS INFLUENCING EFFECTIVENESS ON APPLES 
CONCENTRATION 
So far as known at the present time the directions for use accom- 
-panying all the proprietary commercial preparations are calculated to 
give a spray solution of 10 parts per million (p. p.m.) or 0.001 percent 
concentration of active ingredient. | 
Since effective concentration is related to variety, stage of maturity, 
temperature, and other factors, no inflexible recommendation can be 
made. Some of the results pertaining to concentration are summa- 
rized in table 1. Sprays containing relatively low concentrations of 
active ingredient have proved very effective on summer varieties of 
apple, particularly Williams, Early McIntosh (table 1), and Olden- 
burg (Duchess). Extensive experimental and commercial results indi- 
cate that half-strength sprays (5 p. p. m.) on most summer varieties 
will provide effective control of dropping. With the Williams variety 
even one-fourth strength (table 1) has given satisfactory results. 
TABLE 1.—Relation of concentration of effectiveness of harvest sprays on apples 
Spray State and Spray State and 
Variety concen- Apples: literature Variety concen- apples literature 
tration PP reference tration Pp reference 
P.p.m.| Percent P.p.m.| Percent 
0 78.0 0 21.9 
, Mcin- 2.5 13.6 | tarvtana (7). Wealth 10.0 12.1 || Massachusetts 
pe 5.0 5. Nie 20. 0 Tet Ao G2): 
0 13.0 40.0 3.8 
oe 1. 25 er 0 21.9 
Myilliams. i \ 25 17 laryland (1). MelIntosh______ 2.5 13.1 |‘New York (7). 
5.0 1.8 5.0 TBS 
0 36.8 || Massachusetts p ae New York 
Wealthy______ | 5.0 30.8 ie) PO See ee San ee 
10.0 22.2 | ao 0 19.1 ] 
0 29.6 2.5 829 Haws 
iS eee 5.0 30.9 Do Do-__-.--- 5.0 8.1 ee (4). 
10.0 12.1 | | 10.0 6.1 
3 Although it is impracticable to provide a complete list of dealers, the following partial 
list of companies now oifering such products is furnished for information only, with the 
understanding that no discrimination is intended and no guarantee of reliability is implied : 
California Spray Chemical Corporation, Richmond, Calif.; Dow Chemical Co., Midland, 
Mich. ; Grasselli Chemicals Department, H. I. du Pont de Nemours & Co., Wilmington, Del. ; 
General Chemical Co., New York, N. Y.; Niagara Sprayer and Chemical Co., Middleport, 
N. Y.; The Sherwin-Williams Co., Bound Brook, N. J.; and Westville Laboratories, New 
Haven, Conn. 
