28 BULLETIN 1435, U. S. DEPARTMENT OF AGRICULTURE 
by most of the growers did not vary so much in analysis or in quality 
of material as in the quantity used and number of sprayings. Con- 
sequently, it was believed that value of material used represented a 
method of measurement which reflected rather accurately, on the 
whole, the quantity used. Using the value of spray material per 
tree, there was a range in the six-year average amount used per tree 
in 90 orange groves (Table 23) of from 2 mills to 25 cents, with a 
majority using from 4 to 15 cents worth of material per tree, annually. 
TABLE 23.—Distribution of bearing groves and acreage of bearing trees, by cost of 
spray material per tree ; 
Oranges Grapefruit Tangerines 
Cost per tree of spray material 
Groves Acres Groves Acres Groves Acres 
f Number | Number | Number | Number | Number | Number 
6:cents.and dessa Fok ae ee 38 502 38 277 14 45 
PALO 241 COMES SS hee ee Or ee ieee Ee ee gaa 33 218 35 172 16 30 
I HICeNTS ANGsOV. Cr). ea hae 19 122 20 120 10 10 
TRO Gale ae Se ee ea cece 90 842 93 569 40 85 
Fic. 5.—Spraying is necessary in the growing of thrifty citrus-fruit trees and in the production of 
clean, bright fruit. The most common enemies to be fought in the groves studied were white 
fly, scab, rust mite, thrips, red spider, and melanose 
It was difficult to determine the net effect of the quantity of spray 
material used on yields and price of fruit, because of the variations in 
age and kinds of fruit, quantity of fertilizer used, kind of soil, and 
other factors. A study of the data indicates, however, that the 
growers who sprayed thoroughly had higher yields than the average 
and that cleaner fruit reflected a better price (fig. 5). In 1922, the 
average quantities of concentrated spray materials used per acre 
per annum were, lime-sulphur, 13.8 gallons, and oil emulsion, 6.6 
gallons. 
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