14 
BULLETIN 1288, U. S. DEPARTMENT OF AGRICULTURE 
"Table 4. — Effect of spraying on the yields of tomatoes 
[The spray mixtures used at each locality named were 4-4-50 Bordeaux mixture (4 pounds copper-sulphate 
crystals, 4 pounds stone lime, and 50 gallons water), 4-2-3-50 Bordeaux soap (4 pounds copper-sulphate 
crystals, 2 pounds stone lime, 3 pounds rosin-fishoil soap, and 50 gallons water), and 0.5-0-3-50 copper 
soap (one-half pound copper-sulphate crystals, no lime, 3 pounds rosin-fishoil soap, and 50 gallons water). 
As these spray mixtures were about equally effective, the results of all the sprayed plats are summarized 
in one group.] 
Locality 
Year 
Number of 
piats 
Number 
of 
applica- 
tions 
Yield per acre of 
ripe fruit (pounds) 
Increased yiald 
from spraying 
Sprayed 
Controls 
Sprayed 
Controls 
Pounds 
Per cent 
Salem, N.J 
Riverton, N. J 
Hurlock, Md 
1916 
1917 
1917 
1918 
1918 
1918 
1918 
21 
20 
31 
10 
11 
12 
6 
12 
4 
8 
4 
5 
5 
3 
4 
7 
4 
3 
3 
9,120 
13, 629 
6,233 
3,519 
14, 610 
10, 276 
11, 533 
6,200 
11, 529 
5,343 
2, 750 
12, 487 
9,610 
8,967 
2,920 
2,100 
880 
769 
2,123 
666 
2,566 
47 
18.2 
16.5 
Salem, Va 
Paoli, Ind— 
28 
17 
Riverton, N. J ... 
6.9 
Hurlock, Md 
28.6 
Spraying in areas heavily infested with leaf-spot not only in- 
creases the yield but also improves the quality of the fruit. Defolia- 
tion by leaf-spot deprives the plant of its power to grow and de- 
velop its fruit, for it is in the leaves that it converts the carbon 
dioxide, water, and minerals obtained from the air and soil into foods. 
The new leaves produced at the tips of the branches make some food, 
but not enough. Consequently the fruit of such plants is small, 
watery, and deficient in flavor and solids, especially carbohydrates. 
It is also predominantly yellow instead of scarlet, for the direct 
rays of the sun are too hot for the development of lycopin, the red 
pigment, but favorable for the development of the yellow pigment 
{■) and 4) carotin; hence leaf-spot causes considerable loss in quality 
as well as in yield of fruit, but this loss may be largely prevented by 
spraying. Full directions for spraying tomatoes for the control of 
leaf -spot have been published in Circular Xo. 4 of the Office of Cot- 
ton, Truck, and Forage Crop Disease Investigations, Bureau of 
Plant Industry (7). 
Dusting has some advantages over spraying, but it is not usually 
so effective for the control of tomato leaf-spot. The relative cost 
of the equipment and the ease of application are greatly in its favor. 
A small hand duster (fig. 8) is fairly satisfactory for a small tomato 
acreage, as with it one man can do the work and often at a time 
when it would be difficult to go into the field with a spray machine. 
It is therefore easier to make the applications at proper intervals. 
For larger acreages power dusters are essential. 
The present limitations of dusts are due largely to their less effec- 
tive covering and sticking qualities and consequent poorer control 
of diseases. A dust should form a uniform film, or coating, on the 
foliage, adhere well, and prevent parasites from infecting the plant 
through the dusted parts. It should also possess such chemical and 
physical properties that it will continuously renew the coating where 
the film is broken by the growth or enlargement of the leaves. 
Moreover, it should withstand weathering. Dry Bordeaux mixture 
made with an excess of lime forms a rather uniform coating on the 
